Allison Transmission 1000/2000 Operator`s Manual

WARNING: To help avoid injury and/or property damage caused by unexpected vehicle movement, do not attempt to engage P (Park) with the vehicle in motion (2 km/hr (1 mph) or higher). If you attempt to engage P (Park) with the vehicle in motion (2 km/hr (1 mph) or higher), the park pawl will ratchet, will not engage, and will not hold the vehicle. Repeated park pawl ratcheting can cause transmission damage.

WARNING: If the vehicle has four­wheel­drive and the transfer case is in Neutral, the vehicle can be free to roll even if the P (Park) position is selected. To help avoid injury and/or property damage caused by unexpected movement of the vehicle, be certain that the transfer case is in “high” drive range, not Neutral, whenever the vehicle is parked.

WARNING: If the vehicle is equipped with a two­speed axle or two­speed transfer case which is engaged in “low”, even very low vehicle speeds can produce appreciable transmission output shaft speed. Even the slightest vehicle motion can deter engagement of the park pawl in such cases. To help avoid injury and/or property damage caused by unexpected vehicle movement, be certain that the axle or transfer case is in “high” drive range whenever the vehicle is parked and the park pawl is engaged.

3.21.1 Torque Lock. If the vehicle is parked on an incline and P (Park) is properly engaged, the weight of the vehicle may generate an excessive amount of torque on the park pawl in the transmission. In this situation, it may be difficult to shift the transmission out of the P (Park) position. This condition is commonly called “torque lock.” To alleviate torque lock, do the following:

1. Taking the vehicle’s weight into consideration, push the vehicle uphill a small amount to release the pressure on the park pawl and permit a shift out of P (Park).

2. Shift the transmission out of P (Park) while applying the service brakes.

3. Release the parking brake.

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