The Allison AT 545 automatic transmission includes a hydraulic torque converter, a planetary gear train, and a hydraulic control system. The control system automatically changes gears. The control system provides pressure in order to apply the clutches. With the transmission in the drive range, the torque converter multiplies the engine torque in order to start the movement of the vehicle. The converter also acts as a hydraulic cushion between the engine and the transmission. The clutches and the gear sets provide multiple speeds forward and one speed reverse.

Automatic up shifting and down shifting depends on the vehicle load, the speed, and the foot pressure on the accelerator. When the pedal is fully depressed, the automatic up shifting occurs near the governed engine speed. A partially depressed accelerator pedal causes up shifts to occur at a lower engine speed.

The automatic transmission shift control consists of three components: a range selector mounted in the cab, a shift control lever which is part of the transmission, and an adjustable cable that connects the range selector and the shift control lever.

This section details the service procedures for supporting vehicles for the Allison Automatic Transmission AT 545. Allison Transmission also provides a publication for the testing, servicing, overhaul, and troubleshooting diagnosis of the AT 545 transmission. The name of the publication is the Allison AT 500 and AT 1500 Series Transmission Service Manual SA 1241.

Obtain a copy of the Allison AT 500 and AT 1500 Series Transmission Service Manual SA 1241 from any local Allison distributor or dealer. Order the Service Manual SA 1241 and Allison automatically sends the latest printing of that service manual.

Contact the local Allison distributor for additional information and guidance on overhaul procedures and services.

For the overhaul and the internal parts inspection of the AT 545 automatic transmissions, refer to the Allison AT 500 and AT 1500 Series Service Manual SA 1241 and the Allison AT 545 Inspection Analysis Technicians Guide SA 1948.