AOD

DESCRIPTION
This unit is a 4 speed automatic transmission incorporating an integral overdrive feature. The design of the transmission features a split torque path in third gear, where 40% of the engine torque is transmitted hydraulically through the torque converter and 60% is transmitted mechanically through solid connections (direct drive input shaft) to the driveshaft. When the transmission is in overdrive (4th gear), 100% of engine torque is transmit through the direct drive input shaft.

OPERATION
With selector lever in 1 position, the transmission will start and remain in first gear until the selector lever is moved to another position. In 3 position, the transmission will automatically shift through 1-2-3 range, but will not engage overdrive. In D position, the transmission will automatically select the appropriate time to shift into overdrive (4th gear). The torque converter operation is similar to other types of automatic transmissions, but has an added damper assembly and input shaft for 3rd gear and overdrive.

CONSTRUCTION

Cross Sectional View Of Ford Automatic Overdrive Transmission:

The transmission consists essentially of a torque converter assembly, compound planetary gear train, and a hydraulic control system. For gear control the transmission has four friction clutches, two one-way roller clutches, and two bands. Overdrive is accomplished by the addition of a band to lock the reverse sun gear while driving the planet carrier. The direct drive input shaft couples the engine directly to the direct clutch. This shaft is driven by the torque converter cover through the damper assembly which cushions engine shock to the transmission.