4R70E/4R75E - Automatic Transaxle/Transmission

Transmission Fluid Cooler

CAUTION: Whenever the transmission has been overhauled or a remanufactured transmission has been installed, the transmission fluid cooler tubes and the transmission fluid coolers must be cleaned and backflushed to remove any contaminants or repeat transmission failure will occur.

NOTE: Cleaning and backflushing the transmission fluid cooling system along with following all the normal cleaning and inspection procedures during disassembly and reassembly will keep contamination from reentering the transmission and causing a repeat repair.

When internal wear or damage has occurred in the transmission, metal particles, clutch plate material or band material may have been carried into the torque converter and transmission fluid cooler. These contaminants are a major cause of recurring transmission troubles and must be removed from the system before the transmission is put back into use.

Transmission Fluid Cooler Flow Test

NOTE: The transmission linkage/cable adjustment, fluid level and line pressure must be within specification before carrying out this test.

1. Remove transmission fluid level indicator from transmission fluid filler tube.
2. Place funnel in transmission fluid filler tube.
3. With the vehicle in NEUTRAL, position it on a hoist. Refer to Maintenance/Service and Repair.
4. Remove the transmission fluid cooler return tube (top fitting) from the fitting on the transmission case.
5. Connect one end of a hose to the transmission fluid cooler return tube and route other end of the hose up to a point where it can be inserted into the funnel at the transmission fluid filler tube.
6. Remove the safety stands and lower the vehicle. Insert end of hose into the funnel.
7. Start the engine and run it at idle with the transmission in NEUTRAL.
8. When transmission fluid flows from the hose in a steady stream, a liberal amount of transmission fluid should be observed. "Liberal" is about 1L (1 qt) delivered in 15 seconds. If a liberal flow is observed, the test is complete.
9. If the flow is not liberal, stop the engine. Disconnect the hose from the transmission fluid cooler return tube and connect it to the converter outlet fitting (bottom fitting) on the transmission case.
10. Repeat Steps 6 and 7. If flow is now approximately 1L (1 qt) in 15 seconds, refer to Transmission Fluid Cooler Backflushing and Cleaning. If the flow is still not approximately 1L (1 qt) in 15 seconds, repair or install pump and/or converter.