3T40 Transmission parts, repair guidelines, problems, manuals
Transmission general data
The 3-speed automatic transmission GM 3T40 named as Turbo-Hydramatic 125C was installed on FWD cars with engine capacity from 2 up to 3.1 liters. The first modifications of this transmission did not have the torque converter, later versions (1995) had an electronic control and letter E was added to a new name GM 3T40E. The most significant modification was introduced in 1984. Since then sets of gaskets and seals have not been changed.
| Number of gears | Transmission Type | Drive | Torque (Nm) | ATF (full capacity) L | ATF (change) L | ATF type |
|---|---|---|---|---|---|---|
| 3 | AT | FWD | 250 | 8,5 | 3,8 | Dexron III |
Technical issues and repair guidelines
The GM 3T40 is a reliable, simple transmission that operates over 300 thousand kilometers. It served as a prototype for the 4-speed family 4T40E -4T60E.This transmission rarely gets in repair services. The main spare parts ordered for repair of this transmission are the repair kit of gaskets and seals (Overhaul kit) or a complete Masterkit (with clutches and seals).
Which cars run with this gearbox?
| Brand | Model | Year | Type | Engine |
|---|---|---|---|---|
| Buick | CENTURY/CENTURY WAGON | 95-96 | 3 SP FWD | L4 2.2L |
| Buick | SKYLARK | 95 | 3 SP FWD | L4 2.3L |
| Chevrolet/GM | BERETTA/CORSICA | 95-96 | 3 SP FWD | L4 2.2L |
| Chevrolet/GM | CAVALIER | 95-01 | 3 SP FWD | L4 2.2L |
| Chevrolet/GM | LUMINA | 95 | 3 SP FWD | V6 3.1L |
| Oldsmobile | ACHIEVA | 95 | 3 SP FWD | L4 2.3L |
| Oldsmobile | CUTLASS CIERA/CRUISER | 95-96 | 3 SP FWD | L4 2.2L |
| Oldsmobile | SILHOUETTE | 95 | 3 SP FWD | V6 3.1L |
| Pontiac | GRAND AM | 95 | 3 SP FWD | L4 2.3L |
| Pontiac | SUNFIRE | 95-02 | 3 SP FWD | L4 2.2L |
| Pontiac | TRANS SPORT | 95 | 3 SP FWD | V6 3.1L |
Instruction manuals and useful links
| Link type | Source | Description |
|---|---|---|
| shop.ukrtrans.biz | Manual ATSG 3T40, 125C | |
| shinseiauto.com | Transmission breakdown illustration 125C | |
| at-manuals.com | Diagnosis and general service 125C | |
| web | Sonnax | GM 125C Checkball Locations |