4L60E/700R4 Corvette Servo Piston Assembly, Cover & Snap Ring

Inside a GM 4L60E, 4L65E, 4L70E or 700R4, the second-gear servo is the piston that applies the 2-4 band. When the band apply gets weak you feel it as a soft, drawn-out 1-2 shift, a flare between first and second, or a slip that shows up worse once the fluid is hot. This is the Corvette-style servo, which uses a larger apply area than the small factory piston so the band clamps with more force and the 2-4 shift comes in firm instead of mushy.

The assembly comes complete with the servo piston, the cover, and the snap ring, so nothing has to be robbed off your old part. Manufacturer part number AP037. It fits the whole 700R4 / 4L60E family from 1982 through 2014, which covers Silverado, Sierra, Tahoe, Suburban, Escalade, Blazer, Camaro, Corvette and the rest of the GM rear-drive lineup that ran these transmissions.

Installation is done on the side of the case through the servo bore, with the transmission still in the vehicle. Most guys have it in and out in about thirty minutes with a prybar, a flathead screwdriver, a 10mm socket and a set of large channel-lock pliers: pop the cover and snap ring, pull the old servo, drop the new one in, and seat the ring. One caution from the bench, and it matters: make sure the snap ring is fully seated flush in its groove before you drive. If it is left even slightly proud it can walk out under load and blow the servo out of the case. Seat it right and it holds. This is a strong, cheap fix to try on a high-mileage 4L60E before committing to a full rebuild. Ships from the USA.