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.
If your Silverado, Tahoe, Camaro or built 700R4 flares on the 3-4 upshift, slips in overdrive when you lean on it at highway speed, or keeps cooking 2-4 bands, the 4th gear servo is the part to look at. This super hold servo kit replaces the overdrive apply piston in the GM 700R4, 4L60, 4L60E, 4L65E and 4L70E with a larger-area piston built to the same geometry as the Sonnax 77767K, so the 2-4 band clamps harder at the same line pressure.
The 4L60E uses one band, the 2-4 band, wrapped around the reverse input drum. It is applied by a stacked servo assembly in a bore on the side of the case. In 2nd gear, 2nd apply oil pushes the inner piston to tighten the band. On the 2-3 shift, servo release oil strokes the servo off so the band lets go while the 3-4 clutch takes over. On the 3-4 shift, 4th apply oil acts on the outer 4th gear piston and reapplies the band against release pressure. That last step is the weak link: the stock 4th piston has limited area, so in a heavy truck, a tow rig or anything with more than stock power, the band can slip on the 3-4 and in overdrive. Sonnax notes that these units often show poor 3-4 shift quality and band failure in performance use, and its dual-piston design adds about 40 percent more apply area to fix it.
Scan for codes first. Ratio and pressure codes point elsewhere: an EPC solenoid fault (P0748) or a worn valve body can make every shift soft, and a servo will not fix that. If the only complaint is the 3-4 shift and overdrive slip, check fluid level and condition, then pull the servo cover and inspect the piston seals and band apply pin. Our 4L60E shift problems diagnosis guide walks through which gears use the band and how the solenoid states line up, and the 4L60E common problems guide covers the 3-4 clutch failures that often show up at the same time.
Fits the GM 700R4 (1982 and up), 4L60, 4L60E, 4L65E and 4L70E. That covers the 1993-2013 Silverado 1500, Sierra 1500, Tahoe, Yukon, Suburban, S10, Sonoma, Blazer, Camaro and Corvette, plus swaps and street rods running these units. This is the overdrive (4th) servo only; the 2nd gear apply servo is a separate part. Servo pin length also varies with case and band wear, so plan to measure it. Find the rest of the parts for your build on our 4L60E parts page, or send year and VIN and we will confirm fitment.
If the band is already glazed, replace it while you are in there. The Raybestos Kevlar 2-4 band is the match for a high-clamp servo, and a rebuild kit with frictions, steels and band makes sense if the 3-4 pack has taken heat too.
| 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 |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. This is the 4th gear (overdrive) apply servo only. The 2nd gear piston is a separate part; use it with the OE Corvette-style servo or a matching performance 2nd servo.
On most 4L60E vehicles, yes. The servo sits in a bore on the side of the case under a cover and retaining ring, so it can be swapped in the vehicle once you have clearance.
Check it. A larger apply piston changes pin travel, so measure with a servo pin gauge or dial indicator and select the pin that puts 2-4 band clearance back in spec.
It fixes band slip on the 3-4 and in overdrive. If the flare comes from low line pressure, a worn valve body or a failing EPC solenoid, the servo will not cure it, so check codes and pressure first.
The GM 700R4 from 1982 on, and the 4L60, 4L60E, 4L65E and 4L70E. Send year and VIN if you want us to confirm.
