6T40 Transmission Bonded Clutch Piston Set for GM 6-Speed

A replacement set of bonded clutch pistons for the GM 6T40 family of front-wheel-drive six-speed automatics (6T40, 6T45, 6T45E). Bonded pistons have the sealing lip molded directly to the steel piston, so there is no separate lip seal to roll or pinch during assembly. The set is supplied as pictured; compare the pistons to the ones you pull out of the case before you commit to the build.

The 6T40 and 6T45 are found in the Chevrolet Cruze, Malibu, Sonic, Trax and Equinox, the Buick Verano, Encore and LaCrosse, and the GMC Terrain. On high-mileage units the original piston rubber hardens and weeps, which shows up as clutch slip, flare on the 1-2 or 2-3 shift, delayed engagement, and adapt values that keep climbing. Soft parts kits often skip the pistons, so this is the part that turns a reseal into a real overhaul.

On the bench: with the unit torn down, remove the return spring retainer using a spring compressor (a DT-47799 style tool makes this far easier), lift the old piston out and clean the bore with no scoring left behind. Lube the new bonded lip with ATF or assembly lube, start it square and press it down evenly by hand, then reinstall the spring and retainer. Air check each clutch before the unit goes back in the car, and run the transmission adapt relearn with a scan tool after installation.