Oversized 4th gear apply servo for GM 700-R4, 4L60, 4L60E, 4L65E and 4L70E units that adds clamping area to the 2-4 band and firms up the 3-4 shift.
This is the 4th gear (overdrive) apply servo that goes into a GM 700-R4, 4L60, 4L60E, 4L65E or 4L70E, 1982 and up. It carries a larger apply piston than the factory servo, so it puts more clamping force on the 2-4 band for a given line pressure. Built to the same larger-bore geometry as the Sonnax 77767K super-hold servo, it is the piston most builders swap in when they want the 3-4 shift to hold under load instead of slipping.
On these units a worn or undersized 4th gear servo shows up as a soft or flaring 3-4 upshift, 2-4 band slip on the highway, and eventually a burnt band and shredded servo seals. The extra apply area of this piston tightens up that shift and takes some of the wear off the band, which is worth doing on trucks, tow rigs, and any built 4L60E making more than stock power.
It installs in the overdrive servo bore on the case, the same location as the stock 4th apply servo, using the factory return spring and retaining ring. This is the overdrive (4th) servo only; the 2nd gear apply servo is a separate part. Set your 2-4 band clearance and check servo pin travel when you install it. Fits 700-R4 (1982-up), 4L60, 4L60E, 4L65E and 4L70E.
| Fits | GM 700-R4 (1982-up), 4L60, 4L60E, 4L65E, 4L70E |
| Function | 4th gear / overdrive band apply servo (2-4 band) |
| Design | Oversized apply piston, larger contact area than stock for more holding force |
| Interchange | Built to Sonnax 77767K super-hold servo specs |
| Material | Machined alloy piston with fitted seal |
| Note | Overdrive servo only; 2nd gear servo sold separately. Set 2-4 band clearance on install. |
| Ships from | USA |
