A/T - Diagnosis Information, Lo-Reverse Clutch
89pontiac09Bulletin Number: 89-7-27
Reference Number: 977113
Publish Date: 5/89
DIAGNOSIS INFORMATION ON THE THM
Subject: 125C/HYDRA-MATIC 3T40 LO-REVERSE CLUTCH
Models
Affected: 1980 - 1989 6000, SUNBIRD, GRAND AM AND LEMANS MODELS
Diagnosis information is 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/HYDR-A-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.