Product Overview
This is the DOWNLOAD link for the GM THM 3T40 (125C) Transaxle TechTran covering the transaxle found in many GM vehicles and Opels. Covers transaxle assembly dis-assembly diagnosis and troubleshooting. There have been many engineering changes in this transmission since its introduction. ATSG also has available an "Update Handbook" which includes the many changes and is required along with this manual for a proper overhaul or repair.