Description

The A4LD is a four-speed automatic overdrive transmission with a lockup torque converter.

The 3-4/4-3 shift functions and torque converter clutch lock/unlock are controlled by the Powertrain Control Module (PCM) through a 3-4 shift solenoid and a torque converter clutch solenoid.

The Powertrain Control Module (PCM) electronically controls the torque converter clutch solenoid, which hydraulically operates the piston-plate clutch in the torque converter that provides lockup (solid drive) and unlock functions. The electronics also prevent clutch application in engine modes where noise, vibration or harshness concerns would be most evident in a solid-drive transmission. These modes are:

• Tip-in/tip-out
• Application of brakes
• Closed throttle
• Cold engine
• Very heavy/wide open throttle
• Low engine speed to minimize lugging boom
• 23.5 inches of mercury absolute barometric pressure or below in the intake manifold.

The transmission also provides wide open throttle forced downshifts. When driving in excess of approximately 64 km/h (40 mph) and with the accelerator pedal fully depressed to the floor, the transmission will downshift to second gear for maximum acceleration. If the accelerator pedal is depressed fully to the floor at speeds below 48-56 km/h (30-35 mph) the transmission will downshift to first gear.