8L90 Overhaul Kit 2015, new and ready to install. Fits the 8L90. Ships fast from the USA.
This is a new overhaul kit for a 2015 GM 8L90 eight-speed, the first model year of the unit in the Silverado and Sierra with the 6.2L, the Escalade and Yukon Denali, and the Corvette. It is the soft-parts seal set for a rebuild, plus one hard part that matters: a new bonded piston for the 1-2-7-8-Reverse clutch. If your early 8L90 is leaking, slipping after high mileage, or is already on the bench for a teardown, this kit covers the sealing side of the job.
The 8L90 shifts by applying one of five clutches while releasing another, and every one of those clutches is fed oil through seals: piston lip seals and D-rings, the sealing rings on the rotating shafts, metal-clad seals at the case and pump, and the O-rings and gaskets that keep each feed passage closed. When those harden and leak, apply pressure bleeds off, the clutch slips before it locks, and the control module keeps adding pressure until it sets a ratio or slip code. The kit contents listed for this part are the gaskets, a duraprene pan gasket, O-rings, lip seals, metal-clad seals, sealing rings and small parts, along with the 2015-up 1-2-7-8-Reverse bonded piston. A bonded piston has its sealing lip molded onto the piston, so it replaces the piston and its seal as one part instead of trusting an old piston bore to a new loose seal.
Not every early 8L90 complaint is a seal problem. GM bulletin 18-NA-355 traces the steady-speed shudder between roughly 25 and 80 mph to the torque converter clutch and the fluid, and cures it with a fluid exchange rather than a rebuild. A no-move after a rebuild is usually a pump priming issue, covered in our 8L90 pump failure guide. GEARS Magazine also reports that early 8L units can delay or drop out of gear at a stop because air is trapped in the C5 feed in the stator cover, which GM fixed with an updated stator support and cover. Rule those out with a scan tool and a line pressure test, then use our 8L90 common problems guide to match the symptom to a cause.
This listing is for 2015 8L90 transmissions; the kit itself is catalogued for 2015 and later units. That matters because GM changed the 2-3-4-6-8 clutch in 2018. GEARS reports that the piston, dam and seal grooves were redesigned and the D-rings changed size, for example the main piston D-ring went from 5.515 inch ID on 2015-17 units to 5.505 inch on 2018-up units. A 2015 unit needs the early seals, so measure the 2-3-4-6-8 D-rings in the kit against your old ones before assembly; if a seal has to be forced into its groove, it is the wrong one. The 8L45 does not take this kit. Send us your year and VIN if you are unsure, or compare the 8L90 overhaul kit for 2015-2017 and the rest of the 8L90 and 8L45 collection.
| Fits | 8L90 2015 |
| Part type | Overhaul Kit |
| Condition | New |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. It is the gasket and seal set: gaskets, a pan gasket, O-rings, lip seals, metal-clad seals, sealing rings and small parts, plus a new bonded piston for the 1-2-7-8-Reverse clutch. Frictions and steels are sold separately.
This page is for 2015 units. The kit is catalogued for 2015 and later, but GM changed the 2-3-4-6-8 clutch seals in 2018 and early and late seals are not interchangeable. For a 2018-up truck, check the D-ring sizes against your pistons or send us your VIN first.
A bonded piston has its rubber sealing lip molded directly to the piston. Replacing it removes a common leak path at the 1-2-7-8-Reverse clutch, which applies in first, second, seventh, eighth and Reverse.
GM specifies DEXRON HP licensed fluid for the 8L90 and lists 7.0 liters for a fluid change. The shudder bulletin 18-NA-355 uses Mobil 1 Synthetic LV ATF HP for its fluid exchange. Do not use older DEXRON VI.
Yes. After the rebuild, clear the adaptive values with a capable scan tool, run the service fast learn, then drive the truck through normal upshifts and downshifts so the control module can finish adapting to the new parts.
Usually not. A no-move on a freshly assembled 8L90 is most often an unprimed pump or a pressure regulator assembled backward. Prime the pump with fluid and pre-fill the converter before you suspect the seals.
