8L90 Overhaul Kit 2015-2022, new and ready to install. Fits the 8L90. Ships fast from the USA.
This new overhaul kit covers 2015 through 2022 GM 8L90 eight-speed transmissions and adds something most seal kits leave out: molded pistons. Along with the pistons it carries the gasket set, a reusable oil pan gasket, the sealing ring kit, O-rings and oil seals (kit number KP33900H). Friction and steel plates are not included. It suits a rebuild on an 8L90 from a Silverado or Sierra 1500, Tahoe, Yukon, Escalade, Camaro, Corvette or CT6 where the seals are leaking or the pistons themselves are suspect.
A molded piston has its sealing lip bonded to the piston body, so the seal and piston are replaced as one part. In the 8L90 each of the five clutch packs is applied by a piston, and when a bonded lip hardens, tears or loses its bond, that clutch loses apply pressure in every gear it serves. A plain seal kit cannot fix a bonded piston; you would have to buy the pistons separately. GEARS Magazine notes GM redesigned the 2-3-4-6-8 (C4) piston and its dam piston in 2018 because of cracking, which is exactly the kind of failure that makes a kit with new pistons worth having on the bench.
Rule out the cheaper fixes first. Steady 25 to 80 mph shudder is normally the torque converter clutch reacting to degraded fluid, and GM bulletin 18-NA-355 corrects it with a Mobil 1 Synthetic LV ATF HP fluid exchange. A leak at the front of the case may be a cooler line rather than an internal seal; our 8L90 cooler line guide explains how to tell. For slipping, the 8L90 common problems guide covers line pressure and valve body checks that should come before a teardown.
The kit is listed for 2015-2022 8L90 transmissions, and that range crosses GM's 2018 change to the C4 piston. GEARS Magazine reports early (2015-2017) and late (2018-up) C4 D-rings have different dimensions and are not interchangeable, and the late wave plate does not work with the early piston housing. Before you assemble, match the C4 pistons and seals in the box to the parts from your unit, and do not mix early and late pieces. If you are unsure, send us your year and VIN and we will check it. For an early unit, the 2015-2017 OEM GM kit is a direct early-design option. More parts are on the 8L90 collection page.
| Fits | 8L90 2015-2022 |
| 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.
The kit is sold with molded pistons for the 8L90. Because the C4 piston changed in 2018, lay the kit pistons next to the ones from your unit and confirm they match before assembly.
No. It includes gaskets, a reusable pan gasket, sealing rings, O-rings, oil seals and molded pistons. Clutch plates are bought separately.
It is listed for 2015-2022. Early and late C4 seals are different sizes, so verify the C4 pieces against your unit or send us your year and VIN.
Yes, the kit includes a reusable oil pan gasket. Clean the pan rail and torque the bolts evenly so it seals.
DEXRON HP. Fill from dry, run the engine, set the level hot at the check plug and then run Service Fast Learn.
