42RH

DESCRIPTION

The 42RH is a four speed automatic transmission. Fourth gear is an overdrive range. The transmission is a dual unit design, consisting of a three speed automatic transmission with an overdrive compounder unit attached at the rear. First through third gear ranges are provided by the clutches, bands, overrunning clutch and planetary gear set in the transmission unit. The rear compounder unit provides an overdrive fourth gear ratio of 0.69 to 1. The transmission contains an extra housing in the valve body, which contains the valving and electrical solenoids that provide overdrive fourth gear range. The transmission also utilizes a lock-up torque converter that is controlled by the ECU, and actuated with a solenoid.

OPERATION

Automatic operation of the first three gears is controlled by hydraulics, in the conventional manner. Fourth gear is controlled by a manually operated switch in the instrument panel. The switch is in circuit with the overdrive solenoid and Engine Controller. In the ON position current flows through the switch to the solenoid for the 3-4 shift sequence. The transmission must be in third gear, before a 3-4 upshift will occur. With the control switch in the OFF position, the overdrive solenoid will be defeated, and the 3-4 shift will not occur.