4L85E Shift Kit, new and ready to install. Fits the 4L85E. Ships fast from the USA.
Most 4L85E owners do not want a race shift; they want the transmission in their 2500HD, 3500 or full-size van to stop wearing out the clutch that makes third and fourth. This is the TransGo SK valve body repair kit (the white CORRECTS / PREVENTS / REDUCES box in the photo), the durability kit rebuilders install when a 4L85E comes in with a soft 2-3 shift, no upshifts, or a burned direct clutch. It is new and complete, with no separator plate, because it works with your stock plate.
Line pressure in this transmission is set at the pressure regulator in the pump, and the PCM raises it through the EPC solenoid. That solenoid signal reaches the regulator through the boost valve, a small valve in a bushing that wears with every mile. Once it wears, TransGo says the unit fails one of two ways: boost drops and the direct clutch slips on the 2-3 shift, or boost runs away and breaks the case, direct drum or piston. The SK kit replaces the boost valve and bushing with a hardened, self-cleaning wide land design, adds an EPC boost pressure relief valve, and revises regulator and accumulator springs with a few feed changes in the valve body, case and pump. The result is a slight line pressure increase and shorter shifts that still feel smooth.
A worn valve body bore can mimic a tired boost valve, and a weak pump will drop pressure no matter what kit is installed. Our 4L85E valve body problems and testing guide walks through the pressure checks, and the 4L85E pump failure guide covers what a worn pump looks like. Sonnax also points out that a worn actuator feed limit valve lowers solenoid feed pressure and sets solenoid performance codes, which is why the SK kit includes a tapered actuator filter plug.
TransGo builds a second 4L85E kit, the HD2, sold here as the 4L85E HD2 reprogramming kit. It adds a laminated separator plate that dual feeds the 3rd gear clutch and a higher pressure curve. For a stock truck that tows now and then, the SK is the better match; for constant heavy towing, step up to the HD2.
TransGo lists the SK kit for 1991-2013 GM vehicles with the 4L80E or 4L85E; the 4L85E itself was used from 2002 in GM heavy-duty trucks and vans, including 2004-2009 Chevrolet and GMC models with the 8.1L and 6.0L. The kit instructions split some steps by year and valve body, so follow the section for your unit. If you are not sure whether you have a 4L80E or 4L85E, send us your year and VIN, or browse the 4L85E collection.
| Fits | 4L85E |
| Part type | Shift Kit |
| Condition | New |
| Brand | TransGo |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
TransGo lists a USA-made hardened boost valve and bushing, pressure regulator spacer, washer, springs and snap ring, a stronger 4th feed bolt and washer, direct and reverse feed hole cup seals, the relief valve system with drill bit, accumulator springs, and the actuator filter plug parts.
No. The SK kit gives shorter, firmer shifts with only a slight line pressure increase. It is designed for durability in a daily driven or towing truck.
Some of the work is in the pump and case, so the kit is best installed while the transmission is apart. If the direct clutch is already burned, a rebuild is needed anyway.
Yes. TransGo lists the SK kit for both the 4L80E and the 4L85E from 1991 to 2013 because the two share the same valve body hydraulics.
The filter and pan gasket at minimum. During an overhaul, also replace frictions, steels and seals, and test or replace the pressure control solenoid.
