Reverse Lock-Out

Reverse Lock-out

The TCM is programmed to prevent reverse gear engagement at unacceptable road speeds. The parameters for reverse lock-out are road speed above 5 MPH when the range selector is placed in the R position. When this occurs, the transmission is held in neutral until the speed drops below 5 MPH.

4HP 24: The lock out function is carried out through the combined control of the selector lever (manual valve) and MV 2. MV 2 is responsible for the 2-3 shift but also performs a dual function providing the reverse lock out protection. The solenoid is activated in P N, 2, and 1. When activated, it applies hydraulic pressure to the reverse lock-out spool valve in the valve body. This blocks the flow of hydraulic pressure to the reverse clutch.

A4S 310/270R:





The reverse lock-out function is carried out hydraulically through the reverse lock-out spool valve in the valve body. The reverse lock-out valve controls the flow of hydraulic oil to the reverse clutch. The reverse lock-out valve is controlled hydraulically with the operation of the torque convertor lock-up solenoid (WK). With the WK solenoid activated, hydraulic pressure is applied to the lock-out valve which blocks the flow of hydraulic pressure for the engagement of the reverse gear clutch.

A5S 360R: Similar to the A4S 310/270R, PWM activation of the TCC initiates a hydraulic blocking of reverse gear.

A5S 310Z: The MV 3 solenoid provides reverse lock out protection. The solenoid is normally closed. Power to the MV 3 solenoid is supplied by the EGS control module. The valve is activated by the EGS control module by switching the circuit to ground. When the solenoid is activated, control pressure is applied to the reverse lock out valve, which prevents reverse gear engagement.

A5S 440/560Z: The MV 3 solenoid provides reverse lock out protection. The solenoid is normally closed. Power to the MV 3 solenoid is supplied by the EGS control module. The valve is activated by the EGS control module by switching the circuit to ground. When the solenoid is activated, control pressure is applied to the reverse lock out valve, which prevents reverse gear engagement.