A vehicle equipped with a 4XRE Series Transmission stopped moving suddenly soon after overhaul. Since an unmodified 4XRE valve body does not charge the torque converter in Park, the fluid level was check in the Neutral position, it was over full. The technician then removed the return cooler line to check for cooler flow and there was.
Since cooler flow was present, the pressure regulator valve, filter and pump were deemed good and were supplying the torque converter with fluid. At this time a mechanical failure was considered and the transmission was removed for inspection.
In order to test the transmission for mechanical ability, the turbine shaft splines in the torque converter were checked, they were good. Next, the valve body was removed and the transmission was placed into park. A pair of locking pliers was carefully clamped onto the turbine shaft and air was blown into the forward (rear) clutch feed passage while an attempt was made to turn the turbine shaft in a clockwise rotation. The shaft would not turn which indicated that the transmission was mechanically capable of first gear. Air was then applied to the direct (front) clutch and the rear band in order to check for reverse mechanical ability which was successful.
At this time a decision was made to reinstall the transmission back into the vehicle with another remanufactured torque converter. After placing four (4) quarts of fluid into the transmission, the car was started and four (4) more quarts of fluid were added. This brought the fluid level almost to the full mark which means something is still wrong seeing as the transmission system requires ten (10) quarts of fluid. The vehicle still did not move. At this time a decision was made to remove and inspect the valve body.
It did not take long to find the cause of the no move condition, a piece of debris got the Switch Valve stuck, refer to figure 7.
Looking at the hydraulic schematic in figure 8, converter charge pressure from the pressure regulator valve was directed to the cooler circuit via the stuck switch valve and not to the torque converter. This caused the torque converter not to receive charge oil resulting in the no move condition.
NOTE: Just because you have cooler flow on a 4XRE transmission doesn’t mean the converter was charged with fluid.
The debris was cleaned from the switch valve and checked for full movement in the bore. The vehicle now moved in both directions. An additional two (2) quarts of fluid were added to bring the fluid level up to the correct level.