8L90 Shift Kit, new and ready to install. Fits the 8L90. Ships fast from the USA.
If your Silverado, Sierra, Tahoe, Yukon, Escalade, Express or Corvette with the 8L90 bangs into gears one day and slips the next, runs hot when you tow, or keeps setting P0741 or P0218, the valve body is usually where the trouble starts. This is the TransGo SK 8L90, a USA-made SHIFT KIT valve body repair kit built for the 2015-on 8L90 and 8L45. It replaces the regulator valves that wear and lose control in these units, rather than just raising pressure across the board.
The 8L90 is a clutch-to-clutch eight-speed: there are no bands or one-way clutches doing the timing, so every shift depends on solenoid signal pressure being turned into exact clutch apply pressure by a regulator valve. On the 8L90 that hydraulic control is badly exposed to wear. Sonnax field testing found normal peak line pressure around 315 psi, but units with a worn pressure regulator lineup measured 415 psi and higher, enough to crack the valve body casting at the secondary regulator and shatter drums. TransGo designed SK 8L90 around those exact failures. The kit includes a drop-in pressure regulator and shuttle valve lineup, a drop-in TCC regulator valve, drop-in S2, S3 and S4 regulator valves, an oversize converter feed limit valve and an oversize AFL valve. The new shuttle bushing is meant to stop the casting breakage that a runaway line pressure causes.
Before you pull the pan, rule out the cheap fixes. Shudder at a steady 25-80 mph on many of these trucks is fluid-related, and GM's answer is a complete exchange to Mobil 1 Synthetic LV ATF HP, covered in our 8L90/8L45 shudder and harsh shift guide. Next, scan for solenoid electrical codes and check line pressure against spec. If pressure is high or wanders, or the shudder comes back after a correct fluid exchange, work through our 8L90 valve body symptoms and testing steps. A solenoid that tests bad electrically is a different repair from a worn regulator bore, so do not assume the kit fixes an open circuit.
TransGo lists SK 8L90 for 2015-on 8L45 and 8L90, which covers the full-size GM trucks and SUVs, the 2017-on Express and Savana vans, Camaro, Corvette and Cadillac applications that use this transmission. One revision matters: around 2018 GM changed the S4 regulator valve to a late two-land design (.531 inch inboard land). If your valve body has the late valve, TransGo says to reuse it rather than install the kit's S4 valve. If you are unsure which unit you have, check the transmission ID on the case or send us your year and VIN. You can browse every 8L90 part we carry on the 8L90 collection page.
This is valve body work, done with the valve body on the bench. The kit requires TransGo tool kit AFL-G2-TK, a reamer and guide used to open the converter feed limit and AFL bores for the oversize valves. Ream at low speed with plenty of WD-40 and let the reamer cut. The solenoids look identical but flow differently, so each one must go back in the bore it came out of. Reuse the original retainers, and torque the valve body bolts to 71 lb-in. Because a valve body is rarely the only tired part in a high-mileage 8L90, many builders install the kit during an overhaul with an 8L90 master rebuild kit, and replace suspect solenoids with an 8L90 seven-piece solenoid kit while everything is apart. Refill with DEXRON HP approved fluid such as Mobil 1 LV ATF HP.
After installation, clear all codes and adapts, then run the transmission relearn with a capable scan tool at the correct fluid temperature. Follow with a long road test at normal throttle so each shift can adapt.
| Fits | 8L90 |
| 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 rates SK 8L90 for all 2015-on 8L90 and 8L45 transmissions. The one thing to check is the S4 regulator valve: on later units with the two-land S4 valve, you keep the original S4 valve and install the rest of the kit.
Yes. The kit requires TransGo tool kit AFL-G2-TK to ream the converter feed limit and AFL bores for the oversize valves. It is the same tool used on TransGo's GM and Ford six-speed FWD Gen2 and Gen3 kits, so a shop may already own one.
It addresses the hydraulic causes: TCC regulator wear, loss of converter feed and low cooler flow. If your shudder is from contaminated fluid, do the Mobil 1 LV ATF HP fluid exchange first. A converter with a damaged clutch lining still needs to be replaced.
The kit is a repair kit, not a race calibration. Its job is to restore control of line and clutch pressure, which fixes both the harsh high-line shifts and the soft slipping shifts that worn valves cause.
Clear all DTCs and adapts, run the relearn with a scan tool at the correct fluid temperature, then road test under normal driving. TransGo notes adaptation can stall with active codes or with the fuel tank below 1/4 or above 3/4.
