A/T - Inoperative Lo-Reverse Clutch Diagnosis
89oldsmobileSUBJECT DIAGNOSIS INFORMATION ON THE THM
125C/HYDRA-MATIC 3T40 LO-REVERSE CLUTCH
MODELS/YEARS ALL 1980-89 MODELS EQUIPPED WITH THM
125/125C/HYDRA-MATIC 3T40 TRANSAXLES (M34- MD9)
NUMBER: 89-T-67
CORP. REF. NO: 977113
DATE: April 1989
SECTION: 7A
BULLETIN COVERS:
Diagnosis information given for possible inoperative lo-reverse clutch assembly used in the THM 125C/HYDRA-MATIC 3T40 transaxle.
Causes for an inoperative lo-reverse assembly are as follows:
In the Direct Clutch area:
^ Direct clutch drum center seal that is rolled and/or cut.
^ This condition would cause a cross circuit leak that would apply (drag) the lo-reverse clutch each time the vehicle is driven in the third gear range.
^ Driven sprocket support seals - check for improperly cut angles.
In Lo-Reverse Clutch area:
^ Rolled and/or cut lo-reverse clutch piston seals.
^ Cup plug seal (improperly installed) or cut.
^ Cut "O" ring seal on lo-reverse pipe.
^ Bent and/or leaky lo-reverse pipe.
^ Bent and/or missing lo-reverse pipe bracket.
Part Non Conformity:
^ Porosity in the # 4 and # 5 check ball area of the case cover (cross channel leak during 3rd gear apply).
^ # 6 check ball not seated during apply.
^ Stuck boost valve.
^ Backing plate out of location.
Whenever a suspect lo-reverse condition exists, all of the previous items should be inspected and/or replaced if necessary.
SERVICE MANUAL REFERENCE:
Whenever service to the lo-reverse clutch assembly is necessary refer to the THM 125C/HYDRA-MATIC 3T40 Unit Repair Section of your Service Manual.
SERVICE NOTES:
The direct clutch in the THM 125C/HYDRA-MATIC 3T40 is only applied in 3rd gear and reverse - the reverse clutch is on in the manual lo and reverse gear ranges. If a lo-reverse condition exists the direct clutch assembly should be inspected and all components discussed under Bulletin Covers.