4L60E Bonded Clutch Piston Set, 3-Piece 1994-Up

A set of the three rubber-bonded clutch pistons from the input drum of a GM 4L60E: the 3-4 clutch piston (the smallest of the three), the forward clutch piston (the large one with the drive teeth), and the overrun clutch piston (the large one with the check ball). The sealing lips are molded directly onto the piston, so there are no separate lip seals to roll or cut during assembly. The set is the 1994-up design and also fits 4L65E and 4L70E input drums.

Replace these pistons when a drum air check shows a leak, or when the unit came in slipping in third and fourth, burning the 3-4 pack, or slow to engage Drive. Old pistons take a set with heat and age, and a piston that bleeds apply pressure is one of the most common reasons a freshly rebuilt 4L60E cooks the 3-4 clutches again. On a rebuild with the drum already apart, new bonded pistons are cheap insurance against a comeback.

On the bench: compress the return spring assembly, remove the snap ring, and pull the old pistons out of the input housing. Clean the bores, lube the bonded lips with assembly gel or clean ATF, and seat each piston square with a lip installer or a thin feeler so the lip does not fold over. Reinstall the spring assembly and snap ring, then air check each circuit before the drum goes back in the case.

Fitment note: these are the 1994-up pistons. To put them in a 1982-1993 700R4 or early 4L60 drum you must also use the updated return spring assembly, GM 24206085.