Hydro-Gear EZT ZC & ZD Zero-Turn Transaxle Service and Repair Manual

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

EZT

®

Integrated Zero-Turn Transaxle

Service and Repair Manual

(ZC & ZD Models)

BLN-52622

December 2008 www.mymowerparts.com

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

TABLE OF CONTENTS

Section Page

Foreword .............................................................................................................................. 1

Description and Operation ................................................................................................. 2

Introduction .................................................................................................................................................. 2

General Description ..................................................................................................................................... 2

Hydraulic Schematic .................................................................................................................................... 3

External Features -EZT ® ......................................................................................................................... 4

Technical Specifi cations ............................................................................................................................... 5

Product Identifi cation ................................................................................................................................... 5

Safety .................................................................................................................................... 6

Personal Safety ............................................................................................................................................ 6

Tool Safety ................................................................................................................................................... 6

Work Area Safety ......................................................................................................................................... 6

Servicing Safety ........................................................................................................................................... 6

Troubleshooting .................................................................................................................. 7

Service and Maintenance.................................................................................................... 8

External Maintenance .................................................................................................................................. 8

Service and Maintenance Procedures ......................................................................................................... 8

Fluids ........................................................................................................................................................... 8

Fluid Volume and Level ................................................................................................................................ 8

Fluid Change Procedure .............................................................................................................................. 9

Purging Procedures ................................................................................................................................... 10

Return to Neutral Setting ............................................................................................................................11

Repair ................................................................................................................................. 12

How To Use This Section ........................................................................................................................... 12

General Instructions ................................................................................................................................... 12

Transaxle Removal .................................................................................................................................... 12

Limited Disassembly .................................................................................................................................. 12

Tools and Torques ...................................................................................................................................... 13

Control Arm and Bypass Arm ..................................................................................................................... 14

Seal Kit Replacement ................................................................................................................................ 15

Cog Brake Assembly .................................................................................................................................. 16

Disc Brake Assembly ................................................................................................................................. 17

Side Cover ................................................................................................................................................ 18

Axle Shaft, Reduction Gears and Expansion Plate .................................................................................... 19

Motor Shaft ................................................................................................................................................ 20

Input Shaft and Bypass Rod ...................................................................................................................... 21

Hydraulic Components .......................................................................................................................... 22-26

Transaxle Installation ................................................................................................................................. 26

Assembly After a Complete Teardown ....................................................................................................... 27

Sealant Application ........................................................................................................... 28

Parts List ...................................................................................................................... 30, 31

Glossary of Terms ....................................................................................................... 32, 33 www.mymowerparts.com

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

FOREWORD

Headquartered in Sullivan, Illinois, Hydro-Gear ® is a world leader in the design, manufacture, and service of quality hydrostatic transaxles for the lawn and garden industry. The mission of our company is to be recognized by our customers and the industry as a world-class supplier and the quality leader in everything we do.

This Service and Repair Manual is designed to provide information useful in servicing and troubleshooting the Hydro-Gear EZT ® Integrated Zero-Turn Transaxle.

Also included is a glossary of terms that are frequently used throughout the industry and in

Hydro-Gear service publications. Understanding terminology is very important!

It is necessary, and a good shop practice, that your service area be equipped with the proper tools and the mechanics be supplied the latest information available. All repair procedures illustrated in this guide are suggested, but preferred methods of repair.

Repair procedures require that the transaxle unit be removed from the vehicle.

This is not a certifi cation, test or study guide for a certifi cation test. If a technician is interested in certifi cation, they should contact an agent representing OPEESA (Outdoor Power Equipment and Engine Service Association) at (860)

767-1770 or their Hydro-Gear Central Service

Distributor. Many distributors will be hosting certifi cation testing. These study guides will cover most of the products and manufacturers in our industry.

For more information about Hydro-Gear or our products, please contact your Central Service

Distributor, or call our Customer Service Department at (217) 728-2581.

EZT ® www.mymowerparts.com

1

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

SECTION 1. DESCRIPTION AND OPERATION

INTRODUCTION

The purpose of this manual is to provide information useful in servicing the Hydro-Gear ® Integrated Zero-Turn Transaxle (EZT ® ). This manual includes the EZT’s general descriptions, hydraulic schematics, technical specifi cations, servicing and troubleshooting procedures.

The transaxle normally will not require servicing during the life of the vehicle in which it is installed. Should other servicing be required, the exterior of the transaxle will need to be thoroughly cleaned before beginning most procedures. Do not wash the transaxle while it is hot. Do not use a pressure washer to clean the unit.

GENERAL DESCRIPTION

The EZT is a self contained unit designed for the transfer and control of power. It provides an infi nitely variable speed range between zero and maximum in both forward and reverse modes of operation.

This transaxle uses a variable displacement pump with a maximum displacement of 10cc per revolution, and motor with a fixed displacement of 10cc per revolution. The variable displacement pump features a trunnion mounted swashplate with a direct-proportional displacement control. Reversing the direction of the swashplate reverses the fl ow of oil from the pump and thus reverses the direction of the motor output rotation. The pump and motor are of the axial piston design and utilize spherical nosed pistons which are held against a thrust race by internal compression springs.

The EZT has a self contained fl uid supply and an internal fi lter. The fl uid is forced through the fi lter by a positive “head” on the fl uid in the housing/expansion tank with an assist by the negative pressure created in the pump pistons as they operate.

The check valves in the center section are used to control the make-up fl ow of the fl uid to the low pressure side of the loop.

A cam style, block lifting bypass is utilized in the EZT to permit moving the vehicle for a short distance at a maximum of 2 m.p.h. (3.2 Km/h) without starting the engine.

WARNING

Actuating the bypass will result in the loss of hydrostatic braking capacity. The machine must be stationary on a level surface and in neutral when actuating the bypass.

2

Figure 1. Hydraulic Schematic www.mymowerparts.com

EZT ®

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

EZT ® HYDRAULIC FLOW SCHEMATIC

Figure 2. Hydraulic Flow Illustration

HYDRAULIC SCHEMATIC

Figure 2 provides an illustration of the hydraulic oil circuit. The oil supply for the hydraulic system of the EZT ® is also utilized for lubricating the components of the fi nal drive assembly.

The input shaft and pump cylinder block are turned in one direction only by the engine/ drive belt/pulley combination. Output of the oil fl ow is controlled by the direction and amount that the variable swashplate is angled. As the pump pistons compress they force the oil to fl ow through one of two passageways (forward or reverse) in the center section to the motor cylinder block and motor shaft. Since the motor has a fi xed displacement angle it is forced to turn with the fl ow of oil. As the angle of the pump swashplate is increased the amount of oil being pumped will increase and cause a higher speed output of the motor. Reversing the angle of the pump swashplate will reverse the direction of oil fl ow.

During the operation of the transaxle, fl uid is “lost” from the hydraulic loop through leak paths designed into the product for lubrication purposes (around pistons, under the rotating cylinder blocks, etc.). This “lost” fl uid returns to the transaxle housing, then is pulled back into one of the check valves depending upon the direction of vehicle operation. All of this oil must pass through an internal fi lter.

The motor cylinder block mounts onto a splined motor shaft which drives the gear train.

The bypass feature in the EZT has a mechanical lever which lifts the motor block off of the center section running surface. This allows oil fl ow from the cylinder blocks to be discharged.

EZT ® 3 www.mymowerparts.com

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EXTERNAL FEATURES EZT

®

AXLE SHAFT

MAIN HOUSING

BYPASS ARM

4

FILL PORT

INPUT SHAFT

CONTROL ARM

SIDE COVER

BRAKE ARM

FAN

PULLEY

COG BRAKE DISC

AXLE SHAFT www.mymowerparts.com

EZT ®

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

TECHNICAL SPECIFICATIONS

Technical specifi cations for the EZT ® are listed in Table 1.

Input Speeds

Maximum: 3000 RPM

Minimum: 1800 RPM

Table 1. Technical Specifi cations

Weight of Unit

29 lbs. (13 Kg)

Table 2. EZT Component Options

Component

Axle Shaft Diameter and End Options:

Brake Location:

Brake Type:

Control Arm Location:

Control Arrangements:

Overall Transaxle Reduction:

Component Options

1˝ Flange

Inboard

Cog

Inboard

Standard Control Arm

19.2:1

1˝ DD

Outboard

Disc

Outboard

RTN (scissor style)

21.2:1

PRODUCT IDENTIFICATION

The model and confi guration of the EZT can be determined from the label shown in Figure 3.

EZT ®

Figure 3. Confi guration Label www.mymowerparts.com

5

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

SECTION 2. SAFETY

This symbol points out important safety instructions which, if not followed, could endanger the personal safety and/or property of yourself and others. Read and follow all instructions in this manual before attempting maintenance on your transaxle. When you see this symbol - HEED ITS WARNING.

WARNING

POTENTIAL FOR SERIOUS INJURY

Inattention to proper safety, operation, or maintenance procedures could result in personal injury, or damage to the equipment. Before servicing or repairing the EZT ® , fully read and understand the safety precautions described in this section.

PERSONAL SAFETY

Certain safety precautions must be observed while servicing or repairing the EZT. This section addresses some of these precautions but must not be considered an all-inclusive source on safety information. This section is to be used in conjunction with all other safety material which may apply, such as:

1) Other manuals pertaining to this machine,

2) Local and shop safety rules and codes,

3) Governmental safety laws and regulations.

Be sure that you know and understand the equipment and the hazards associated with it.

Do not place speed above safety.

Notify your supervisor whenever you feel there is any hazard involving the equipment or the performance of your job.

Never allow untrained or unauthorized personnel to service or repair the equipment.

Wear appropriate clothing. Loose or hanging clothing or jewelry can be hazardous. Use the appropriate safety equipment, such as eye and hearing protection, and safety-toe and slip-proof shoes.

Never use compressed air to clean debris from yourself or your clothing.

TOOL SAFETY

Use the proper tools and equipment for the task.

Inspect each tool before use and replace any tool that may be damaged or defective.

WORK AREA SAFETY

Keep the work area neat and orderly. Be sure it is well lit, that extra tools are put away, trash and refuse are in the proper containers, and dirt or debris have been removed from the working areas of the machine.

The fl oor should be clean and dry, and all extension cords or similar trip hazards should be removed.

SERVICING SAFETY

Certain procedures may require the vehicle to be disabled in order to prevent possible injury to the servicing technician and/or bystanders.

The loss of hydrostatic drive line power may result in the loss of hydrostatic braking capability.

Some cleaning solvents are fl ammable. Use only approved cleaning materials: Do not use explosive or fl ammable liquids to clean the equipment.

To avoid possible fi re, do not use cleaning solvents in an area where a source of ignition may be present.

Discard used cleaning material in the appropriate containers.

6 EZT ® www.mymowerparts.com

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

SECTION 3. TROUBLESHOOTING

WARNING

Do not attempt any servicing or adjustments with the engine running.

Use extreme caution while inspecting the drive belt assembly and all vehicle linkage!

Follow all safety procedures outlined in the vehicle owner’s manual.

In many cases, problems with the EZT ® are not related to a defective transaxle, but are caused by slipping drive belts, partially engaged bypass valves, and loose or damaged control linkages.

Be sure to perform all operational checks and adjustments outlined in Section 4, Service and Maintenance, before assuming the pump is malfunctioning. Table 3 below provides a troubleshooting checklist to help determine the cause of operational problems.

Table 3. EZT Troubleshooting Checklist

Possible Cause Corrective Action

UNIT OPERATES IN ONE DIRECTION ONLY

Control linkage bent or out of adjustment

Drive belt slipping or pulley damaged

Repair or replace linkage, Page 8

Repair or replace drive belt or pulley, Page 8

VEHICLE DOES NOT DRIVE/TRACK STRAIGHT

Vehicle tires improperly infl ated

Control linkage bent or out of adjustment

Bypass assembly sticking

Refer to vehicle manufacturer suggested pressure

Repair or replace linkage, Pages 8 and 11

Repair or replace bypass, Page 21

Oil level low or contaminated oil

Excessive loading

Loose parts

Bypass assembly sticking

Air trapped in hydraulic system

UNIT IS NOISY

Fill to proper level or change oil, Page 9

Reduce vehicle loading, Page 8

Repair or replace loose parts

Repair or replace linkage

Purge hydraulic system, Page 10

UNIT HAS NO/LOW POWER

Engine speed low

Control linkage bent or out of adjustment

Drive belt slipping or pulley damaged

Oil level low or contaminated oil

Excessive loading

Bypass assembly sticking

Air trapped in hydraulic system

Adjust to correct setting

Repair or replace linkage, Page 8

Repair or replace drive belt or pulley, Page 8

Fill to proper level or change oil, Page 9

Reduce vehicle loading, Page 8

Repair or replace linkage

Purge hydraulic system, Page 10

Debris buildup around transaxle

Cooling fan damaged

Oil level low or contaminated oil

Excessive loading

Air trapped in hydraulic system

Damaged seals, housing, or gaskets

Air trapped in hydraulic system

UNIT IS OPERATING HOT

Clean off debris, Pages 2 and 8

Repair or replace cooling fan

Fill to proper level or change oil, Page 9

Reduce vehicle loading, Page 8

Purge hydraulic system, Page 10

TRANSAXLE LEAKS OIL

Replace damaged component

Purge hydraulic system, Page 10

EZT ® 7 www.mymowerparts.com

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SECTION 4. SERVICE AND MAINTENANCE

NOTE: Any servicing dealer attempting a warranty repair must have prior approval before conducting maintenance of a Hydro-Gear ® product unless the servicing dealer is a current Authorized

Hydro-Gear Service Center.

EXTERNAL MAINTENANCE

Regular external maintenance of the EZT ® should include the following:

1. Check the vehicle operator’s manual for the recommended load ratings. Insure that the current application does not exceed load rating.

2. Check oil level in accordance with Figure 4

Page 9.

3. Inspect the vehicle drive belt, idler pulley(s), and idler spring(s). Insure that no belt slippage can occur. Slippage can cause low input speed to the transmission.

4. Inspect the vehicle control linkage to the directional control arm on the transaxle. Also insure that the control arm is securely fastened to the trunnion arm of the transaxle.

5. Inspect the bypass mechanism on the transaxle and the vehicle linkage to insure that both actuate and release fully.

SERVICE AND MAINTENANCE

PROCEDURES

Some of the service procedures presented on the following pages can be performed while the EZT is mounted on the vehicle. Any repair procedures as mentioned in the repair section of this manual must be performed after the unit has been removed from the vehicle. The unit should be thoroughly cleaned before any service procedures are performed.

FLUIDS

The fl uids used in Hydro-Gear products have been carefully selected, and only equivalent, or better products should be substituted.

Typically, an engine oil with a minimum rating of 9.0 cSt (55 SUS) at 230° F (110° C) and an

API classifi cation of SL is recommended. A

20W50 engine oil has been selected for use by the factory and is recommended for normal operating procedures.

FLUID VOLUME AND LEVEL

Fluid volume information is provided in Table

4.

Certain situations may require additional fl uid to be added or even replaced. Refer to Page 4 for the proper fi ll port location.

Fill the EZT so the oil level is .75”-1.50” (19-38 mm) below the oil fi ll port.

Recheck the fl uid level once the unit has been operated for approximately 1 minute.

Purging will be required. Refer to the purging procedures on Page 10.

8 EZT ® www.mymowerparts.com

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FLUID CHANGE

FLUID CHANGE PROCEDURE

This transaxle is factory fi lled, sealed and does not require oil maintenance. However, in the event of oil contamination or degradation, oil addition or change may alleviate certain performance problems.

1. Remove the transaxle from the vehicle.

NOTE: If removing the wheel from the transaxle, do so by removing the four (4)

lug nuts. Do not remove the axle/hub nut.

2. Clean the oil fi ll port area of any debris.

3. Remove the oil fi ll port fi tting.

4. Position the transaxle so the oil will drain completely out of the housing.

5. Fill the transaxle at the oil fi ll port according to Figure 4.

6. Install the oil fi ll port fi tting.

7. Purging will be required. Refer to the purging procedures on Page 10.

8. Recheck the fl uid level once the unit has been operated for approximately 1 minute.

Fluid Description

20W50 engine oil

Table 4. Fluid Volumes for the EZT ®

Volume

52.4 fl . oz. (1550 ml) to 55.8 fl . oz. (1650 ml)

TOP OF FILL PORT

0.75” - 1.50” (19-38mm) depth at 50°-100°F (10°-38°C)

OIL LEVEL

EZT ®

Figure 4. Fluid Level and Fill Port www.mymowerparts.com

9

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

PURGING PROCEDURES

Due to the effects air has on effi ciency in hydrostatic drive applications, it is critical that it is purged from the system.

These purge procedures should be implemented any time a hydrostatic system has been opened to facilitate maintenance or any additional oil has been added to the system.

Air creates ineffi ciency because its compression and expansion rate is higher than that of the oil approved for use in hydrostatic drive systems.

The resulting symptoms in hydrostatic systems may be:

1. Noisy operation.

2. Lack of power or drive after short term operation.

3. High operation temperature and excessive expansion of oil.

Before starting, make sure the transaxle/transmission is at the proper oil level. If it is not, fi ll to the specifi cations outlined on Page 9, Figure

4.

The following procedures should be performed with the vehicle drive wheels off the ground, then repeated under normal operating conditions.

1. With the bypass valve open and the engine running, slowly move the directional control in both forward and reverse directions (5 or

6 times), as air is purged from the unit, the oil level will drop.

2. With the bypass valve closed and the engine running, slowly move the directional control in both forward and reverse directions (5 to

6 times). Check the oil level, and add oil as required after stopping the engine.

3. It may be necessary to repeat Steps 1 and

2 until all the air is completely purged from the system. When the transaxle moves forward and reverse at normal speed purging is complete.

10 www.mymowerparts.com

EZT ®

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

RETURN TO NEUTRAL SETTING

WARNING

POTENTIAL FOR SERIOUS INJURY

Inattention to proper safety, operation, or maintenance procedures could result in personal injury, or damage to the equipment. Before servicing or repairing the EZT ® , fully read and understand the safety precautions described in this section.

WARNING

Do not attempt any servicing or adjustments with the engine running.

Use extreme caution while inspecting the drive belt assembly and all vehicle linkage!

Follow all safety procedures outlined in the vehicle owner’s manual.

The return to neutral mechanism on the transmission is designed to set the directional control into a neutral position when the operator releases the vehicle hand control. Follow the procedures below to properly adjust the return to neutral mechanism on the transaxle:

1. Confi rm the transaxle is in the operating mode (bypass disengaged). Raise the vehicle’s drive tires off the ground to allow free rotation.

NOTE: It may be necessary to remove the drive wheel from the axle hub to access the linkage control and the transaxle return arm.

Remove the wheel by removing the four (4) lug nuts. Do not remove the axle/hub nut.

2. Remove the Original Equipment Manufacturer’s (OEM’s) control linkage at the control arm.

Refer to Figure 5.

3. Start the engine and increase the throttle to

AXLE ROTATION “A”

AXLE

ROTATION

“B”

AXLE

ROTATION

“A” full engine speed.

4. Check for axle rotation. If the axle does not rotate, go to Step 5. If the axle rotates, go to

Step 6.

5. Stop the vehicle’s engine. Reattach and adjust the OEM linkage according to Step 3 and Step 4. Stop the vehicle engine. Refer to Figure 5.

6. Note the axle directional movement. Stop the vehicle engine. Loosen the RTN adjustment screw until the control arm can be rotated.

Rotate the control arm in the opposite direction of the wheel rotation in 5 degree increments.

Tighten the RTN adjustment screw. Refer to table 6. Required Torque values, page 14.

Recheck according to steps 3 and 4. Stop the vehicle engine. Reattach and adjust the

OEM linkage according to the OEM manual.

Recheck according to steps 3 and 4. Refer to

Figure 5.

AXLE ROTATION “B”

15° 15°

RTN Adjustment Screw

Speed and Directional Control

EZT ®

Figure 5. Return to Neutral Setting www.mymowerparts.com

11

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

SECTION 5. REPAIR

HOW TO USE THIS MANUAL

Each subassembly illustrated in this section is illustrated with an exploded view showing the parts involved. The item reference numbers in each illustration are for assembly instruc-

tions only. See page 31 for part names and descriptions. A complete exploded view and item list of the transaxle is provided at the end of the repair section.

GENERAL INSTRUCTIONS

Cleanliness is a primary means of assuring satisfactory life on repaired units. Thoroughly clean all exposed surfaces prior to any type of maintenance. Cleaning of all parts by using a solvent wash and air drying is usually adequate. As with any precision equipment, all parts must be kept free of foreign material and chemicals.

Protect all exposed sealing surfaces and open cavities from damage and foreign material. The external surfaces should be cleaned before beginning any repairs.

Upon removal, it is recommended that all seals,

O-rings, and gaskets be replaced. During installation lightly lubricate all seals, O-rings and gaskets with a clean petroleum jelly prior to assembly. Also protect the inner diameter of seals by covering the shaft with a cellophane

(plastic wrap, etc.) material.

Parts requiring replacement must be replaced from the appropriate kits identifi ed in the Items

Listing, found at the end of this manual. Use only original Hydro-Gear ® replacement parts found in BLN-51427 (CD).

IMPORTANT: When internal repair is performed on the EZT ® , the fi lter assembly must be replaced.

TRANSAXLE REMOVAL

It is necessary to remove the EZT from the vehicle before performing the repair procedures presented in this section.

NOTE: If removing the wheel from the transaxle, do so by removing the four (4)

lug nuts. Do not remove the axle/hub nut.

LIMITED DISASSEMBLY

The following procedures are presented in the order in which they must be performed to completely disassemble the unit. Do not disassemble the unit any farther than is necessary to accomplish the required repairs. Each disassembly procedure is followed by a corresponding assembly procedure.

Reassembly is accomplished by performing the “Assembly” portions of the procedures. If the unit has been completely disassembled, a summary of the assembly procedures, in the order in which they should occur, is given on page 27.

12 www.mymowerparts.com

EZT ®

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

Miscellaneous

EZT ® Service & Repair Manual

Flat Blade Screw Driver (2)

Torque Wrench

Air Impact Wrench

Rubber Mallet

Breaker Bar

Side Cutters/Snips

Pliers

Needle Nose

Large External Snap Ring

Small Internal Snap Ring

TOOLS AND TORQUES

Table 5. Required Tools

Sockets

1/2”-3/8” Adapter

3/8” Deep

1/2” Deep

7/16” Deep

9/16” Deep

3/4” Deep

13/16” Deep

7/8”

T-25 Torx Head

T-40 Torx Head

Apex AN-08

Metal Plug

Side Housing Screws

Center Section Bolts

Control Arm Stop Stud

Control Arm Screw

Stop Stud Nut

Check Plugs

Expansion Plate Screws

Brake Assembly Screw

Hub Nut

Fan/Pulley Lock Nut

Breather Fitting

RTN Adjustment Screw

Disc Brake Screw

Table 6. Required Torque Values

180-240 lb-in [20-27 Nm]

105-155 lb-in [12-17 Nm]

525-700 lb-in [60-80 Nm]

50-120 lb-in [6-18 Nm]

230-310 lb-in [26-35 Nm]

85-120 lb-in [10-14 Nm]

280-400 lb-in [32-45 Nm]

25-50 lb-in [3-6 Nm]

80-120 lb-in [9-14 Nm]

200-220 lb-ft [271-298 Nm]

360-520 lb-in [41-59 Nm]

180-240 lb-in [20-27 Nm]

175-200 lb-in [19-22 Nm]

80-120 lb-in [9-14 Nm]

25

26

56

65

7

9

12

21

73

99

122

126

131

157

Plug 9/16-18

Screw 1/4-20 x 1.25

Screw 3/8-24 x 2.5

Stud 5/16-24

Screw 5/16-24 x 1

Nut, Lock 5/16-24 UNF

Check Plug Assembly

Screw 10-32 x 0.50

Screw 1/4-20 x 1

Nut, Hex 3/4-16 Lock

Lock Nut 1/2 x 20

Fitting 9/16

Screw 5/16-24 x 1

Screw 1/4-20 x 2

EZT ® www.mymowerparts.com

13

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CONTROL ARM AND BYPASS ARM

Refer to Figure 6.

Disassembly

1. Loosen and remove the lock nut (26) and fl at washer (24). Discard the lock nut (26) and fl at washer (24).

2. Remove the torx head screw (25) from the directional control.

3. Remove control arm (23) and pucks (22).

Discard the pucks.

4. Remove the bypass arm retaining ring (18) and bypass arm (17). Discard the retaining ring.

5. If necessary, remove and replace the control arm stop stud (21).

Inspection

1. Inspect the control arm stop stud (21) for wear or damage.

2. Inspect the control arm (23) for wear or damage.

3. Inspect the bypass arm (17) for wear or damage.

Assembly

1. Install the bypass arm (17) onto the bypass rod. Secure the bypass arm with a new retaining ring (18).

2. Replace the control arm stop stud (21) if removed. Torque according to specifi cations in Table 6 on page 13.

3. Install the control arm (23).

4. Install the control arm screw (25). Refer to

Table 6 for screw torque specifi cations.

14

Figure 6. Control Arm and Bypass Arm www.mymowerparts.com

EZT ®

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

Before disassembly, wipe the unit free of any debris to avoid contamination.

Refer to Figure 7.

Input Seal

1. Remove the input pulley from the input shaft.

2. Remove the seal retaining ring (34).

3. Carefully pull the input seal (33) out of the housing bore with a “hook” type tool. Care must be taken to avoid damage to the housing bore or shaft sealing area.

4. Lubricate the new seal with petroleum jelly prior to installation.

5. Wrap the shaft keyway (splines) with cellophane to prevent damage to the seal lip during installation.

6. Slide the seal over the shaft and press it into the housing bore.

7. The seal should seat against the spacer.

8. Install the seal retaining ring (34) and make sure it is fully seated in its groove.

Output Seal

1. The seal (51) can be replaced by following steps 2-6 of the procedure used to replace the input seal.

2. Install the retaining ring (34) and make sure it is fully seated in its groove.

Motor Shaft Seal

1. Remove the brake assembly. See pages

16-17.

2. The seal (10) can be replaced by following steps 3-6 of the procedure used to replace the input shaft.

SEAL KIT REPLACEMENT

Trunnion Seal

1. Remove the control arm and any attachments to the control arm. See page 14.

2. The seal (20) can be replaced by following steps 3-6 of the procedure used to replace the input shaft.

Bypass Seal

1. Remove the bypass arm and any attachments to the bypass arm. See page 14.

2. Remove the seal retaining ring (16). Remove the bypass rod, keeping the retaining ring (14) attached. Remove the bypass rod seal (13). Deburr the bypass rod.

3. Install the seal (13). Install the bypass rod with the retaining ring (14) attached. Install the seal retaining ring (16).

Figure 7. Seal Kit Replacement

EZT ® 15 www.mymowerparts.com

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COG BRAKE ASSEMBLY

Refer to Figure 8.

Disassembly

1. Remove the control arm and bypass arm.

See page 14.

2. Remove the oil from the transaxle. See page

9.

3. Remove the brake arm spring (75), if installed. Remove the brake arm screw(s)

(73), washer(s) (72), brake arm (74) and bushing(s) (71).

4. Remove the retaining ring (14) and cog brake disc (100).

5. Remove the motor shaft lip seal (10), if removing the side housing.

Inspection

1. Check the brake arm and cog brake disc for excessive wear or teeth damage. Replace if necessary.

2. Check for excessive looseness at the arm pivot point.

Assembly

1. Install the motor shaft lip seal (10), if removed. Refer to page 15. Remember to use a seal protector during installation.

2. Install the cog brake disc (100) and retaining ring (14).

3. Install the bushing(s) (71), brake arm (74), washer(s) (72) and brake arm screw(s) (73).

Torque screws to 80-120 in-lbs (9-14 Nm).

4. Install the brake arm spring (75), if removed.

5. Fill the transaxle with new oil. See page 9.

6. Install the bypass arm and control arm. See page 14.

16

100

14

74

71

75

73

72

73

72

71

10

Figure 8. Cog Brake Assembly www.mymowerparts.com

EZT ®

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

Refer to Figure 9.

Disassembly

1. Remove the control arm and bypass arm.

See page 14.

2. Remove the oil from the transaxle. See page

9.

3. Remove the brake arm bias spring (75).

4. Remove the cotter pin (160), castle nut (159) and washer (158).

5. Remove the brake arm (74), compression spring (156) and two brake pins (155).

6. Remove the brake yoke assy screws (73

& 157), the spacer (154), brake yoke assy

(153), puck plate (151), outer puck (150), rotor (100) and inner puck (150).

7. Remove the motor shaft lip seal (10), if removing the side housing.

Inspection

1. Check the brake disc and pucks for excessive wear. Replace if necessary.

DISC BRAKE ASSEMBLY

2. Check for excessive looseness at the arm pivot point.

Assembly

1. Install the motor shaft lip seal (10), if removed. Refer to page 15. Remember to use a seal protector during installation.

2. Install the inner puck (150), rotor (100), outer puck (150) and puck plate (151).

3. Install the brake yoke assy (153), brake pins

(155), spacer (154) and the brake yoke assy screws (73 & 157).

4. Install the compression spring (156), the brake arm (74), the washer (158), the castle nut (159) and the cotter pin (160).

5. Install the brake arm bias spring (75).

7. Fill the transaxle with new oil. See page 9.

8. Install the bypass arm and control arm. See page 14.

EZT ®

160

100 10

74

157

75

158

154

153

151

73

153

2X 155

156

2X 150

159

Figure 9. Disc Brake Assembly www.mymowerparts.com

17

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

SIDE COVER

Refer to fi gure 10.

Disassembly

1. Remove the control arm and bypass arm.

See page 14.

2. Remove the oil from the transaxle. See page

9.

3. Remove the brake assembly. See pages 16 and 17.

4. Remove the motor shaft lip seal. See page

15.

5. Remove the side housing screws (9) and belt defl ector (144), if installed.

6. Pull the side housing (68), leaving the axle

(49) and bull gear (46) assembled in the main housing. It may be necessary to use pry tools at the pry points to break loose the sealant (positions 1-16 and 4-6, Figure

10).

7. Clean off all the old sealant on the side and main housings. Take care not to damage the sealing surfaces. A wire brush and solvent is effective.

Inspection

1. Inspect the bearing and bushing areas of the side cover.

Assembly

1. Apply a bead of sealant around the perimeter of the side housing face. See sealant pattern on page 28.

2. Install the locating pins (8), if not already installed.

3. Install the side housing (2). Use care not to smear the sealant bead.

4. Install the side housing screws (9) and belt defl ector (144, if used). Refer to the screw tightening pattern in Figure 10 and torque specifi cation in Table 6 on page 13.

5. Install the remaining seals. Refer to page

15. Remember to use a seal protector during installation.

6. Install the brake assembly. See pages 16 and 17.

7. Fill the transaxle with new oil. See page 9.

8. Install the bypass arm and control arm. See page 14.

18

16X 9

68

14

12

10

8

6

2X 8

66

1

16

144

3

5

7

Figure 10. Side Cover www.mymowerparts.com

9

11 13

15

4

2

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Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

AXLE SHAFT, REDUCTION GEARS AND EXPANSION PLATE

Refer to Figure 11.

3. Inspect the axle shaft, bearing and bushing.

Disassembly

4. Inspect the expansion plate.

1. Remove the bypass arm and control arm.

See page 14.

Assembly

2. Remove oil from the transaxle. See page

9.

3. Remove the side cover. See page 18.

1. Apply a small bead of sealant to the expansion plate area of the housing. See page 28.

Install the expansion plate (53). Torque the screws according to Table 6.

4. Remove the spiral retaining ring (45), bull gear (46), inboard sleeve bearing (48) and washer (47).

2. Reassemble and install the reduction gears

(42 & 43), jack shaft pin (44) and washers

(41).

5. Remove the reduction gears (42 &43), jack shaft pin (44) and washers (41).

6. Remove seal retaining ring (34), seal (51), axle (49) and bushing (50).

3. Install the bull gear (46), retaining ring (45), bearing (48) and washer (47) onto the axle

(49).

7. If necessary, remove the expansion plate assembly (53).

4. Install the axle (49) and bushing (50) into the housing (1).

5. Install the axle seal (51) and retaining ring

(34).

NOTE: Expansion plate removal will typically destroy the plate. Clean all sealant from the expansion plate area.

6. Install the side cover. See page 18.

7. Install all remaining seals. See page 15.

Inspection

8. Fill the transaxle with oil. See page 9.

1. Inspect the bull gear for wear or damage.

2. Inspect the reduction gears, jack shaft pin and washers.

9. Install the bypass arm and control arm. See page 14.

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Figure 11. Axle Shaft, Reduction Gears and Expansion Plate www.mymowerparts.com

19

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

MOTOR SHAFT

Refer to Figure 12.

Disassembly

1. Remove the control arm and bypass arm.

See page 14.

2. Drain the oil from the transaxle. See page

9.

3. Remove the side cover. See page 18.

4. Remove the reduction gears. See page

19.

5. Remove fl at washer (36), motor shaft and pinion gear (39 & 38) and fl at washer (40).

Inspection

1. Inspect the motor shaft (39), pinnion gear

(38) and fl at washers (36 & 40) for wear or damage.

Assembly

1. Insert the motor shaft (39) with the pinnion gear (38) and fl at washers (36 & 40) into the center section (57).

2. Install the reduction gears. See page 19.

3. Install the side cover. Refer to page 18.

4. Install new seals. Refer to page 15.

5. Fill the transaxle with oil. See page 9.

6. Install the bypass arm and control arm. See page 14.

20

Figure 12. Motor Shaft www.mymowerparts.com

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Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

INPUT SHAFT AND BYPASS ROD

Refer to Figure 13.

Disassembly

1. Remove the control arm and bypass arm.

See page 14.

2. Drain the oil from the transaxle. See page

9.

3. Remove the side cover. See page 18.

4. Remove the reduction gears. See page

19.

5. Remove the motor shaft. See page 20.

6. Remove the retaining ring (34) and shaft seal (33). Discard the seal.

7. Remove the spacer (32) and input shaft assembly (29, 30 & 31).

8. Remove the compression spring (27) and washer (28).

9. Remove the rings (14 & 16), bypass rod (15) and seal (13).

Inspection

1. Inspect the input shaft components and bypass rod for wear or damage.

Assembly

1. Visually ensure that the pump block is aligned concentrically with the center section running face.

2. Install the compression spring (27) and washer (28).

3. Insert the input shaft (29), with bearing (30) and retaining ring (31), into the pump block assembly. NOTE: Do not force the shaft and bearing as damage may occur. If alignment is correct, the shaft assembly will fi t into place.

4. Install the washer (32), seal (33) and retaining ring (34). Use a seal protector when

EZT ® installing the input shaft seal.

5. Deburr the end of the bypass rod. Install the bypass rod (15), retaining ring (14), seal (13) and retaining ring (16).

6. Install the motor shaft. See page 20.

7. Install the reduction gears. See page 19.

8. Install the side cover. See page 18.

9. Install new seals in the side housing. See page 15.

10. Fill the transaxle with oil. See page 9.

11. Install the bypass arm and control arm. See page 14.

Figure 13. Input Shaft and Bypass Rod Assembly www.mymowerparts.com

21

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

HYDRAULIC COMPONENTS

Refer to Figures 14-23.

Disassembly

1. Remove the bypass arm and control arm.

See page 14.

2. Drain the oil from the transaxle. See page

9.

3. Remove the side cover. See page 18.

4. Remove the reduction gears. See page

19.

5. Remove the motor shaft. See page 20.

6. Remove the input shaft and bypass rod. See page 21.

7. (See Figure 14) Remove the swashplate

(19) and pump cylinder block (4) as one assembly. NOTE: Removal will be aided by applying a small amount of pressure on the trunnion mounted swashplate towards the center section. Also note that the control arm

(23, page 30) may be loosely assembled at this point to assist in swashplate removal.

While gently removing the swashplate and block assembly, keep the block face fl ush with the center section to minimize damage to the running surface.

8. (See Figure 15) Disassemble the pump cylinder block (4) from the swashplate (19).

9. (See Figure 16) Check each piston for proper operation by pressing the pistons in and releasing them in the block bore. Disassemble the pump cylinder block. Check for piston/block wear in the cylinder bore.

Inspect the pistons (A), piston springs (C) and thrust washers (B) for excessive wear or damage. NOTE: Thrust washers may be held in place in the piston by residual oil.

10. Reassemble the pistons, springs and washers into the cylinder block and set aside.

11. (See Figure 17) Remove the thrust bearing assembly (35) from the swashplate (19).

(Center Section/Filter)

12. (See Figure 18) Remove the center section mounting screws (12). NOTE: The center section is under motor block piston spring pressure. These screws are factory installed to 700 lb-in (80 Nm) and use an anaerobic thread adhesive. A breaker bar will be required at this step. Clean the internal threads of the mounting holes with compressed air.

13. Remove the center section and fi lter assembly (57, Figure 19). NOTE: Bypass plate (Figure 20) may slide out of the center section.

14. Remove the fi lter cover by pressing in and down on the fi lter cover tabs. Discard the cover.

15. Note the location of both check plugs (56) before removal for correct replacement during reassembly. Remove and inspect the check plug assemblies (56) for debris or damage.

16. Remove the fi lter base (61) and discard it.

NOTE: The fi lter base is included in the fi lter kit to be installed during reassembly of the unit.

(Motor Block)

17. (See Figure 21) Remove the motor cylinder block assembly (6) from the housing (1).

18. Disassemble the motor cylinder block assembly (4). Check each piston for proper operation by pressing the pistons in and releasing them in the block bore. Disassemble the motor cylinder block. Check for piston/block wear in the cylinder bore.

Inspect the pistons, piston springs and thrust washers for excessive wear or damage. NOTE: Thrust washers may be held in place in the piston by residual oil.

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Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

19. Reassemble the pistons, springs and thrust washers into the cylinder block and set aside.

20. Remove the thrust bearing assembly (35) from the housing (1). Inspect the thrust bearing and thrust bearing cavity in the housing.

Inspection

1. Inspect the pump cylinder block running surface for wear or damage.

2. Inspect the swashplate and thrust bearing assemblies for wear or damage.

3. Inspect the center section block running surfaces. NOTE: These “sealing” surfaces should be smooth in appearance without scratches, scoring, nicks or abrasions. Drag a fi ngernail across the surface to detect uneven wear or scratches which may not be visible.

4. Inspect the threaded check plug ports of the center section for debris or damage.

5. Inspect the motor cylinder block running surface for damage and wear.

6. Inspect all bearing, bushing and wear areas in the housing.

Assembly

(Motor Block)

1. (See Figure 21) Turn the housing (1) so the motor thrust bearing cavity is facing up.

This will assist in the installation of the motor thrust bearing assembly (35) keeping it in the bearing cavity during installation of the center section assembly (57, Figure 19).

2. Insert the thrust bearing (35) in the housing

(1). NOTE: Place the thin race of the bearing towards the housing bearing cavity. The thick race must face the pistons.

HYDRAULIC COMPONENTS

(Center Section/Filter)

3. (See Figure 20) Install the new fi lter base

(61) onto the center section (57).

4. It will be necessary to clean the check plugs prior to re-assembly. Install the check plugs

(56), in their correct location, into the center section (57). Tighten the check plugs according to Table 6.

5. Align the tabs on the fi lter cover with the slots in the fi lter base and carfully press the cover onto the base until the tabs snap into place. Insure the bypass plate (Figure 20) is located properly in the center section.

6. (See Figures 12 & 22) Install the motor shaft (39), pinion gear (38) and fl at washers

(36 & 40) into the center section (57).

7. Assemble the motor block assembly (6) onto the motor shaft (39).

8. (See Figure 22) Install the motor shaft, center section and motor block assembly into the housing so that the motor block pistons contact the thrust bearing race.

NOTE: Hold in place and insure all pistons are still positioned correctly in the cylinder bore by confi rming spring bias against the center section.

9. (See Figure 18) After applying thread adhesive, insert the center section mounting screws (12) while holding downward pressure on the center section assembly (57,

Figure 22).

10. Tighten the center section mounting screws

(12) to the proper torque. Refer to Table

6. NOTE: The center section must be fully seated into the pilot bore before the screws are tightened. The center section will not self locate.

EZT ® 23 www.mymowerparts.com

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

(Swashplate/Pump Block)

11. (See Figure 17) Install the pump thrust bearing (35) in the trunnion machined swashplate (19). NOTE: Place the thin race of the bearing towards the swashplate. The thick race must face the pistons.

12. (See Figure 15) Place the pump block assembly (4), pistons down, on top of the thrust bearing in the swashplate (19).

13. Coat the pump running surface with clean motor oil.

14. Care must be taken to prevent the scaring or scratching of the center section sealing

face during this step. Insert the shaft of the swashplate/pump block assembly (Figure

23) into the housing while simultaneously compressing the pistons in the block.

NOTE: To assist in the installation of these components, insert the assembly until 3/4 of the pump block is covered by the center section. Then slightly press the shaft end toward the center section while pushing the shaft into its bore.

15. Install the input shaft and bypass rod. See page 21.

16. Install the axle shaft, reduction gears and expansion plate, if removed. Refer to page

19.

17. Install the side cover and brake. See pages

16-18.

18. Fill the transaxle with new oil. See page

9.

19. Install the bypass arm and control arm. See page 14.

Figure 14.

Figure 15.

A

B

C

4

19

35

24

Figure 16.

www.mymowerparts.com

EZT ®

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

Figure 17.

Figure 20.

1

Figure 18.

35

Figure 21.

6

EZT ®

Figure 19.

www.mymowerparts.com

25

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

TRANSAXLE INSTALLATION

1

6

19

57

39

Use the following procedure to complete the installation of the transaxle on the vehicle.

1. Install and secure the transaxle on the vehicle according to the instructions in the vehicle owner’s manual.

2. With the vehicle raised, install the wheels on the axles, and snug the wheel hardware.

3. Lower the vehicle wheels to the ground and torque the wheel hardware per the vehicle owner’s manual.

4

38

Figure 22.

Figure 23.

26 www.mymowerparts.com

EZT ®

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

ASSEMBLY AFTER A COMPLETE TEARDOWN

If the unit has been torn down completely, the following summary identifi es the assembly procedures necessary to completely assemble the unit. Each assembly procedure is located by a page reference.

3. Install the axle shaft, reduction gears and expansion plate. See page 19.

4. Install the cog brake and side cover. See page 16-18.

5. Fill the transaxle with new oil. See page 9.

The part reference numbers provided in each assembly procedure are keyed to the individual exploded views, and are also keyed to the complete unit exploded view on page 30.

6. Install the bypass arm and control arm.

See page 14.

7. Install the transaxle onto the vehicle.

1. Install the hydraulic components. See pages 22-26.

8. Perform the purge procedures listed on page 10.

2. Install the input shaft and bypass rod. See page 21.

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27

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

SEALANT APPLICATION

NOTE: Prior to applying the new sealant, the old sealant must be removed from all surfaces.

A small consistent bead of the sealant around the housing face will be suffi cient. Use sparingly.

The illustration below indicates the correct areas.

28 www.mymowerparts.com

EZT ®

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

NOTES

EZT ® www.mymowerparts.com

29

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

EZT

®

EXPLODED VIEW

30

DISC BRAKE

BRAKE KIT

MOUNT

P

TO

CLEVIS PIN

BRAKE KIT

Figure 24. EZT ® www.mymowerparts.com

THROUGH HOLE

BRAKE KIT

W/ SPRING

BRAKE KIT

EZT ®

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

No.

DESCRIPTION

1

2

3

4

ASSEMBLY, MAIN HOUSING

BUSHING

ASSEMBLY, SIDE COVER

BUSHING

PLATE, BYPASS

ASSEMBLY, PUMP BLOCK

BLOCK, CYLINDER

PISTONS

SPRINGS, COMPRESSION

WASHERS, THRUST

SPACER

ASSEMBLY, MOTOR BLOCK

PLUG, 9/16-1

PIN, STAINLESS, HEADLESS

HFHCS 1/4-20 X 1.25 (SELF-TAPPING)

SEAL, LIP

BOLT, HEX FLANGE 3/8-24 X 2.5

SEAL, LIP

RING, RETAINING

ROD, BYPASS

RING, RETAINING

ARM, BYPASS

RING, RETAINING (PUSHNUT)

SWASHPLATE, TRUNNION, MACHINED

SEAL, LIP

STUD

WASHER

ARM, CONTROL

WASHER, FLAT

TWHCS 5/16-24 X 1.0

NUT, HEX LOCK 5/16-24 UNJF

SPRING-HELICAL COMPRESSION

WASHER

SHAFT, INPUT

BEARING, BALL

RING, RETAINING WIRE

SPACER

SEAL, LIP

RING, RETAINING

BEARING, THRUST

WASHER, FLAT

RING, RETAINING

GEAR, PINION, 13T

SHAFT, MOTOR

WASHER, MOTOR SHAFT

WASHER, HT

GEAR, 10T/48T

GEAR, 10T JACKSHAFT

PIN, JACKSHAFT

RING, SPIRAL RETAINING

GEAR, 52T BULL

WASHER

BEARING, SLEEVE (INBOARD)

AXLE

BUSHING

SEAL, LIP

KIT, SEAL

KIT, EXPANSION PLATE

KIT, FAN-PULLEY

43

44

45

39

40

41

42

36

37

38

32

33

34

35

50

51

52

53

46

47

48

49

54

29

30

31

25

26

27

28

21

22

23

24

18

19

20

14

15

16

17

10

12

13

5

8

9

6

7

EZT ® www.mymowerparts.com

EZT

®

ITEMS LIST

No.

DESCRIPTION

140

141

144

150

151

153

154

128

130

131

134

135

138

139

155

156

157

158

159

160

200

120

121

122

123

124

126

127

72

73

74

75

99

100

119

67

68

70

71

64

65

66

60

61

62

63

55

56

57

59

KIT, BRAKE ASSEMBLY

CHECK PLUGS

KIT, CENTER SECTION-FILTER

KIT, BYPASS ARM

ASSEMBLY, COVER

KIT, FILTER

FILTER, BASE

CENTER SECTION

MAGNET

SCREW, 10-32 X 1/2 (SELF-TAPPING)

HOUSING, MAIN

PLATE, EXPANSION

COVER, SIDE

PIN, CLEVIS

BUSHING

WASHER

SCREW

ARM, BRAKE

SPRING

NUT, HEX LOCK

ROTOR

HUB

FAN

PULLEY

NUT, HEX LOCKING

WASHER OR CAPSCREW 1/4-20

HUB KIT

FITTING

HOSE, EXPANSION TANK

CAP, BARBED VENT

NUT, HEX 1/4-20

SPACER OR CAPSCREW 5/16-20 X 1

WASHER

SPRING

KIT, BREATHER ASSEMBLY

KIT, BREATHER ASSEMBLY

ARM, NEUTRAL

RTN

DEFLECTOR, BELT

PUCK, BRAKE

PLATE, PUCK

ASSEMBLY, BRAKE YOKE

SPACER

PIN, BRAKE

SPRING, BRAKE COMPRESSION

CAPSCREW, 1/4-20 X 2.0

WASHER

NUT, CASTLE 5/16-24

PIN, COTTER

KIT, RTN

31

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

GLOSSARY OF TERMS

Axial Piston: Type of design for hydraulic motors and pumps in which the pistons are arranged parallel with the spindle (input or output shaft).

Bantam Duty: A descriptive term relating to the product capacity (meaning: light duty).

Bypass Valve: A valve whose primary function is to open a path for the fl uid to bypass the motor or pump. Also referred to occasionally as the freewheel valve or dump valve.

Case Drain Line (Return Line): A line returning fl uid from the component housing to the reservoir.

Cavitation: A concentrated gaseous condition within the fl uid causing the rapid implosion of a gaseous bubble.

Center Section: A device which acts as the valve body and manifold of the transmission.

Charge Pump: A device which supplies replenishing fl uid to the fl uid power system (closed loop).

Charge Pressure: The pressure at which replenishing fl uid is forced into a fl uid power system.

Charge Relief Valve: A pressure control valve whose primary function is to limit pressure in the charge circuit.

Check Valve: A valve whose primary function is to restrict fl ow in one direction.

Closed Loop: A sealed and uninterrupted circulating path for fl uid fl ow from the pump to the motor and back.

Decay Rate: The ratio of pressure decay over time.

End Cap: See “Center Section”

Entrained Air: A mechanically generated mixture of air bubbles having a tendency to separate from the liquid phase.

Gerotor: A positive displacement pump frequently used as a charge pump.

Hydraulic Motor: A device which converts hydraulic fl uid power into mechanical force and motion by transfer of fl ow under pressure.

Hydraulic Pump: A device which converts mechanical force and motion into hydraulic fl uid power by producing fl ow.

Hydrostatic Pump: See “Hydraulic Pump”

Hydrostatic Transaxle: A multicomponent assembly including a gear case and a hydrostatic transmission.

32 EZT ® www.mymowerparts.com

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

Hydrostatic Transmission: The combination of a hydraulic pump and motor in one housing to form a device for the control and transfer of power.

Inlet Line: A supply line to the pump.

Integrated Zero-Turn Transaxle: The combination of a hydrostatic transmission and gear case in one housing to form a complete transaxle.

Manifold: A conductor which provides multiple connection ports.

Neutral: Typically described as a condition in which fl uid fl ow and system pressure is below that which is required to turn the output shaft of the motor.

Pressure Decay: A falling pressure.

Priming: The fi lling of the charge circuit and closed loop of the fl uid power system during start up, frequently achieved by pressurizing the fl uid in the inlet line.

Purging: The act of replacing air with fl uid in a fl uid power system by forcing fl uid into all of the components and allowing the air a path of escape.

Rated Flow: The maximum fl ow that the power supply system is capable of maintaining at a specifi c operating pressure.

Scoring: Scratches in the direction of motion of mechanical parts caused by abrasive contaminants.

Swash Plate: A mechanical device used to control the displacement of the pump pistons in a fl uid power system.

System Charge Check Valve: A valve controlling the replenishing fl ow of fl uid from a charge circuit to the closed loop in a fl uid power system.

System Pressure: The pressure which overcomes the total resistance in a system, including all effi ciency losses.

Valve: A device which controls fl uid fl ow direction, pressure, or fl ow rate.

Variable Displacement Pump: A pump in which the displacement per revolution can be varied.

Volumetric Displacement: The volume for one revolution.

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33

Hydro Gear Parts or New Units Call 606-678-9623 or 606-561-4983

© 2008 Hydro-Gear

Printed in U.S.A.

Rev. P4

34 www.mymowerparts.com

EZT ®