Automatic Overdrive Transmission (AOD)

DESCRIPTION

Fig. 1 shows the location of the converter, front pump, clutches, gear train and most of the internal parts used in the Automatic Overdrive Transmission.

The Automatic Overdrive Transmission provides fully automatic operation in either the (OD) (overdrive) or D (overdrive lockout) positions. Manual upshifting and downshifting is available through the forward drive positions (OD), D, 1.

NOTE:There is no 2 (second) selector position for an automatic overdrive transmission therefore second gear starts are not available.

(OD) (OVERDRIVE) - This is the normal driving position for an Automatic Overdrive Transmission. In this position the transmission starts in first gear and as the vehicle accelerates, automatically upshifts to second and third gear The upshift to fourth (overdrive) gear will occur as the vehicle approaches the desired highway cruising speed and the driver eases up on the accelerator pedal. The transmission will automatically downshift as vehicle speed decreases.

NOTE: The transmission will not shift into or remain in overdrive gear when the accelerator is pushed to the floor.

The Automatic Overdrive Transmission differs from conventional 3 speed automatic transmissions in that the planetary gear set operates in 4th gear. Some audible perception of planetary action can exist as with any other mechanical device and should be accepted as being commercially quiet unless some abnormal noise is present.

D (OVERDRIVE LOCKOUT) - In this position the transmission operates as in (OD) (OVERDRIVE) except that there is no overdrive (fourth) gear. This position may be used when driving up or down mountainous roads to provide better performance and greater engine braking than the overdrive position. The transmission may be shifted from (OD) to D or D to (OD) at any speed.

1(LOW)-This position can be used when maximum engine braking is desired. To help brake the vehicle on hilly roads where D (OVERDRIVE LOCKOUT) does not provide enough braking, shift the selector lever to 1 (LOW). At vehicle speeds above approximately 20 MPH the transmission will shift to second gear, and remain in second gear. When vehicle speed drops below approximately 20 MPH the transmission will downshift to first gear, and remain in first gear. Upshifts from 1 (LOW) can be made by manually shifting to (OD) (OVERDRIVE) or D (OVERDRIVE LOCKOUT) When 1 (LOW) is used for starting up, the transmission starts in first gear and stays in first gear.

FORCED DOWNSHIFTS-At vehicle speeds from approximately 50 MPH to 20 MPH in (OD) (OVERDRIVE) or D (OVERDRIVE LOCKOUT) the transmission will downshift to second gear when the accelerator is pushed to the floor. At vehicle speeds above approximately 50 MPH the transmission will not downshift to second gear. At vehicle speeds below approximately 20 MPH the transmission will downshift to first gear when the accelerator is pushed to the floor. At most vehicle speeds in (OD) (OVERDRIVE) the transmission will downshift from fourth gear to third gear when the accelerator is pushed for moderate to heavy acceleration.