Automatic Transmission/Transaxle: Description and Operation

Fig. 1 ZF-4 Automatic Transaxle:

The ZF-4 automatic transaxle, Fig. 1, has four forward speeds and one reverse. Third gear ratio is 1:1. Fourth gear is an overdrive range providing an 0.74:1 gear ratio.

NOTE: The transmission and differential are not integral and require different lubricants.

The transaxle consists of a three element torque converter, front mounted oil pump, planetary gear mechanism, roller and sprag clutches, clutch and brake mechanisms and a brake band. The brake band is applied in second and fourth gear ranges by the piston assembly. Transaxle shifting is controlled by a governor valve, a line pressure valve, a throttle pressure regulator valve and a modulator valve. Valve operation is dependent on shift lever position, vehicle speed and throttle position.