January 2000 Issue
Issue Summary:
After TCM replacement on GM diesels, no 3-4 shift or TCC occurs and a code 88 is stored. We explain what caused the code to be set.
GM has made some changes in the PCM on 4L80-E transmissions to eliminate one of the causes of no upshift from first gear.
The malfunction indicator lamp illuminated and DTC P0503 stored on a 4T80-E transaxle may be caused by movement of the final-drive internal ring gear relative to the transaxle case.
In a Chrysler 42RE, a buzzing noise in Reverse may be caused by either a partially clogged main filter or the pressure-regulator valve.
A cracked forward piston or reverse/forward and coast-clutch drum can cause premature coast-clutch failure on GF4A-EL units.
GF4A-EL transaxles with codes 6, 25 and 55 that place the unit in failsafe may require replacement of the PCM.
We also have diagnostic-connector locations and code-retrieval information on GF4A-EL units.
