General Motors 6T40 Gen 3

Transmission general data

The family of 6-speed automatic gearboxes of GM 6T30E, 6T40E, 6T45E "Hydra-Matic" is a state-of-the-art range of FWD gearboxes used on Buick and Chevrolet vehicles from 1.4 to 3.2 lit. The 6T45E found application on FWD and AWD vehicles.

Technical issues and repair guidelines

These gearboxes can operate properly with spare parts of different quality. Standard repair kits of gaskets and seals produced by ATOC often ordered for repair of these gearboxes.In case of ATF overheating it is often required to change all pistons because the rubber gets hard under the influence of the temperature. The set of pistons consists of 5 pieces.

The transmission fluid for these gearboxes should be changed every 40-80 thousand kilometers and checked for opacity every visit to repair services taking into account short service life of solenoids and torque converters (TC) with slippages. In the course of each overhaul, TC is reassembled and the lock-up clutch is replaced, because its wear-out reduces the resource of solenoids.Leaking seal of the TC unit is a sign of possible issues with the pump bushing, which gets damaged by vibrations and wear-out of the TC lock-up.

The construction of this gearbox is conceptually the same with ZF of 6HP series and problems in these gearboxes are caused by the same factors:vibrations which damage bushings. Vibrations lead to situations when ATF leaks through worn-out bushings.This is one more present-day gearbox in which it is important to examine the quality and temperature of ATF. In situation of any apprehensions related to contaminated ATF – change the fluid for protecting the valve body. It is also recommended to keep a wary eye on symptoms of the pressure loss in the line after a long-term operation as well as check and clean the valve body with solenoids. The TC unit repair with replacement of friction discs is required in the situation of rapid ATF pollution and issues with the valve body (especially with the mileage higher than 130-150 thousand kilometers). Overloading with high torques and aggressive accelerations also may have a bad impact on this gearbox.

On the top of everything else, experts recommend to install additional transmission radiator for the whole 6Т range of transmissions. Cars with this transmission manufactured over the last years are adjusted in more cautious way and stop drivers from using the car with neglect to this good 6-speed gearbox, which is capable to compete with Jatco CVTs in terms of comfort.