8L90 Overhaul Kit, new and ready to install. Fits the 8L90. Ships fast from the USA.
This is a complete soft-parts master kit for the GM 8L90 eight-speed automatic. One box holds the gasket set, the overhaul seals and sealing rings, a filter, the friction clutch kit and a steel plate module, which is everything a rebuilder normally orders separately before a full teardown. It is meant for the 8L90 out of a Silverado or Sierra 1500, Tahoe, Yukon or Escalade, Camaro, Corvette or Cadillac CT6 that is slipping, flaring, engaging late or has already put clutch material on the pan magnet. Molded (bonded) pistons are not part of this kit; if a piston is cracked or its rubber is damaged, that piece is a separate purchase.
The 8L90 builds its eight forward ratios with five clutch packs, and every shift is one pack releasing while another applies. Because each clutch works in several gears, one burned pack or one leaking piston seal shows up as a whole family of bad shifts rather than a single one. The gaskets, seals and sealing rings in this kit restore the hydraulic side: they keep apply pressure in each clutch circuit instead of bleeding it to the sump. The frictions and steels restore the mechanical side: the holding capacity of the packs themselves. Doing both together is the point of a master kit. New seals cannot save glazed plates, and new plates fed by tired seals slip again within months.
Not every 8L90 complaint is worn clutches. The well-known 25 to 80 mph rumble-strip feel is torque converter shudder, and GM bulletin 18-NA-355 fixes it with a fluid exchange, not a rebuild. Sonnax has also measured worn valve bodies running more than 415 psi of line pressure against a normal peak near 315 psi, enough to crack castings and burn clutches; rebuilding the clutches without fixing that pressure just repeats the failure. Our 8L90 common problems and fixes guide walks through those checks, and the 3-4 clutch failure guide covers the most common burned pack.
This kit is listed for the 8L90 without a year range, so check it against your unit before ordering. GEARS Magazine reports two changes that matter for soft parts. In 2018 GM redesigned the 2-3-4-6-8 (C4) piston and its seal grooves, and early and late D-rings are not interchangeable. In 2019 the 4-5-6-7-8-R (C5) clutch moved to a spiral-groove friction tied to a calibration change, and those discs are not meant for older units. Compare the C4 seals and C5 frictions in the kit with the parts coming out of your case, or send us your year and VIN. The filter in this kit interchanges with GM 24274402. Other 8L90 parts are on the 8L90 collection page, and if you only need seals, the 2015-2017 OEM overhaul kit is the lower-cost option.
| Fits | 8L90 |
| Part type | Overhaul Kit |
| Condition | New |
| Brand | GM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Yes. It includes a friction clutch kit and a steel plate module along with the gasket set, seals, sealing rings and a filter. Molded pistons and hard parts such as drums and the pump are not included.
The listing does not give a year range. GM changed the C4 piston seals in 2018 and the C5 frictions in 2019, so compare those parts with your unit or send us your year and VIN before ordering.
DEXRON HP. GM lists 7.4 quarts for a fluid change; a rebuilt unit that starts dry takes more, so fill, run it and set the level hot at the check plug.
Yes. Clear adaptives and run Service Fast Learn with a capable scan tool, then drive the vehicle through every gear so the module can finish learning the new clutches.
Usually not on its own. Steady-speed shudder between 25 and 80 mph is typically torque converter shudder that GM addresses with a fluid exchange in bulletin 18-NA-355.
