Bonded rubber-on-steel clutch pistons for the GM 6T40, 6T45 and 6T45E six-speed, used in Cruze, Malibu, Verano and Equinox overhauls.
Rebuilding a 6T40 or 6T45 out of a Chevrolet Cruze, Malibu, Sonic, Trax or Equinox, a Buick Verano or Encore, or a GMC Terrain? Most soft parts kits seal the drums but leave you reusing the original apply pistons, and on this transmission that is a gamble. This is a set of new bonded clutch pistons for the 6T40, 6T45 and 6T45E. The rubber sealing lip is molded onto the steel piston body, so there is no loose lip seal to install. The photo shows the set as supplied: a large outer piston with a notched outer edge and a smaller inner piston marked WT05704. Lay them next to the pistons you pull out of your unit and confirm the match before you start assembly.
The 6T40 has no bands. Every gear comes from two of five clutches being applied together, and each clutch is squeezed by a hydraulic piston riding in its housing. Fluid from the valve body pushes the piston against the clutch pack, and a return spring pulls it back off when the pressure is released. Because shifts are timed hand-offs between clutches, the control module expects each piston to stroke and hold exactly the way it learned. A piston that leaks apply oil makes its clutch slip, and the module answers with a performance code or a flare it cannot adapt out.
Bonded pistons trade a separate seal for a lip vulcanized to the metal. That makes assembly cleaner, but when the rubber shrinks from heat or the steel cracks, the whole piston is scrap; there is no seal to swap.
A piston fault and a solenoid fault set the same performance codes, so rule out the electrical side first with a scan tool and the solenoid cleaning routine. GM's own bulletin on missing gears with P0776, P0796, P0873, P0878, P2714 or P2723 blames a non-functioning pressure control solenoid for many of them. Our 6T40 delayed engagement guide covers the in-car checks, and 6T40 common problems and fixes lists which clutch is applied in each gear so you can tie a slip to a pack. On the bench, slide each old piston in and out of its housing by hand. GEARS points out a heat-shrunk piston gives no drag at all.
The set is listed for the GM 6T40, 6T45 and 6T45E front-wheel-drive six-speeds. GM changed drums, pumps and controls between Generation 1, 2 and 3 units, so compare diameter, notch pattern and lip profile against your originals rather than assuming every year is the same. If you are unsure, send your year and VIN before ordering. Pistons are one part of a complete overhaul; the 6T40E master rebuild kit supplies the frictions, steels and seals around them.
| Transmission | GM 6T40, 6T45, 6T45E (6-speed FWD) |
| Type | Bonded clutch pistons (molded lip seal) |
| Material | Steel piston with bonded rubber |
| Contents | Piston set as pictured |
| Common vehicles | Chevy Cruze, Malibu, Sonic, Trax, Equinox; Buick Verano, Encore; GMC Terrain |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
The set is supplied as pictured, one large outer piston and one smaller inner piston marked WT05704. Compare both to the pistons in your unit before assembly; the listing does not break out a position for each one.
GEARS recommends always replacing the bonded pistons during a 6T40/6T45 rebuild. Heat can shrink the rubber or crack the steel in ways that are hard to see, and a leaking piston means another teardown.
They are listed for the 6T40, 6T45 and 6T45E. Because GM made running changes across three generations, match the pieces to your originals or send us your year and VIN.
Use Dexron VI, set the level at the case check plug with the fluid at 85-95 C, and run the Transmission Adaptive Values Learn with a scan tool. Skipping the learn can leave harsh or flared shifts.
Yes. A performance code for a pressure control solenoid can be caused by a pressure leak in the clutch circuit it controls, including a cracked or shrunk piston.
