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The 8L90 is GM's heavy-duty eight-speed rear-drive automatic. It sits behind the 6.2L V8 in 2015-up Silverado and Sierra 1500s, Tahoes, Suburbans, Yukons and Escalades, behind a lot of 2017-up 5.3L trucks, in the C7 Corvette, the 2016-up Camaro SS and the CTS-V. Its lighter sibling, the 8L45, goes in the Colorado, Canyon and smaller Cadillacs, and takes different parts.
Before anyone buys an 8L90 rebuild kit, they should know one thing: a large share of "my 8L90 needs a rebuild" trucks do not. The famous 8L90 shudder is usually a fluid problem, and the 1-2 clunk is usually a valve body problem. Rule those out first. If the unit really is worn out, here is what to buy.
Rule Out the Two Fixes That Are Not Rebuilds
Shudder at 25-80 mph under light throttle
That is the converter clutch chattering while it slips on and off, and on most 8L90s it traces to the original Dexron VI fill absorbing moisture. GM's fix, published in service bulletin 18-NA-355, is a triple flush with Mobil 1 Synthetic LV ATF HP, the fluid that became Dexron HP. If a triple flush cures the shudder, you just saved the price of a rebuild. Full diagnosis steps are in our 8L90 torque converter shudder fix.
Clunk or bang on the 1-2 or 2-3 shift
Often a worn regulator valve and springs in the valve body. The STL-8L90 valve body fix kit replaces those parts and costs a fraction of a teardown. If the valve body is too far gone, a remanufactured 8L90 valve body is the next step, still without pulling the transmission apart.
If the unit slips, flares between gears, throws P0894 or gear ratio codes, or the fluid is black with glitter in the pan, those fixes will not help. It is rebuild time.
8L90 Layout: What You Are Rebuilding
| Spec | 8L90 |
|---|---|
| Gear ratios (1st / 8th) | 4.56 / 0.65 |
| Reverse | 3.82 |
| Planetary gearsets | 4 |
| Clutch packs | 5 (C1-C5), 21 friction plates total |
| Controls | TEHCM (control module mounted on the valve body, inside the case) |
| Current service fluid | Dexron HP |
The internal control module matters for the rebuild. It stays with the valve body, it does not like heat or debris, and a replacement module has to be programmed to the vehicle. Keep it clean during the teardown and bag it separately. If it has to be replaced, see our 8L90 TEHCM replacement cost breakdown.
Choosing the Kit
| Kit | What It Covers | Best For |
|---|---|---|
| 8L90 Overhaul Kit 2015-2017 | Gaskets, seals, O-rings, sealing rings | Resealing a unit whose frictions measure in spec |
| 8L90 Master Rebuild Kit 2015 | Overhaul kit plus frictions and steels | The default for a slipping or burned unit |
| 8L90 Banner Rebuild Kit 2015 | Master kit plus additional hardware | Tow trucks, overheated units, one-box orders |
| BorgWarner 35445KIT frictions | All 21 frictions across C1-C5 | Pairing OE-supplier friction material with the seal kit of your choice |
Kit contents vary by supplier; check the listing before you order, and match the year range to the build date on the case tag, not just the model year of the truck.
Parts Outside the Kit Worth Checking
- Pump. Scored gears or pocket wear drop line pressure and undo a fresh friction job. Replace with a new 8L90 pump if the clearances are out.
- Clutch drums and module. Look for heat-blued steel, worn splines and cracked feed holes. Replacement clutch modules and drums are available when the originals are cooked.
- Solenoids. A solenoid kit is cheap insurance on a unit that has run on contaminated fluid.
- Internal wiring harness. Check the internal harness for chafed insulation and oil-soaked connectors.
- Thermal bypass valve. A stuck valve cooks fluid; the full-flow replacement for GM 13561467 keeps ATF moving through the cooler.
- Converter and cooler. After a friction failure the converter must be replaced or professionally cleaned and the cooler flushed or replaced. Reinstalling a contaminated converter is the fastest way to lose a new rebuild.
The One Tool People Skip
The 8L90 uses solid Teflon sealing rings on its drums and shafts. Install them without sizing them back down and the drum shaves a ring as it goes into the bore — you will not know until the unit has no apply pressure on that clutch. The 8L90 sealing ring expander and resizer kit installs and resizes those rings so the drum drops in clean. Add a dial indicator for end play and a feeler gauge set for clutch clearances.
After assembly, fill with Dexron HP, set the level hot at the check plug with the engine running, and run the adaptive learn with a bidirectional scan tool. See our 8L90 fluid type and capacity guide for the fill procedure.
Shop 8L90 Rebuild Parts
Overhaul, master and banner kits, BorgWarner frictions, pumps, drums, solenoids and valve bodies for the GM 8-speed. Free shipping on every order.
Shop 8L90 Parts → Core Transmission Parts →FAQ
Does an 8L90 with shudder need a rebuild?
Usually not. Most 8L90 shudder is the converter clutch reacting to moisture-contaminated Dexron VI. GM service bulletin 18-NA-355 calls for a triple flush with Mobil 1 Synthetic LV ATF HP. Try that before buying a rebuild kit.
Will an 8L45 kit fit an 8L90?
No. The 8L45 is a lighter-duty unit with different clutch packs and hardware. Buy parts listed for the 8L90.
How many friction plates are in an 8L90?
Twenty-one, spread across five clutch packs (C1-C5). The BorgWarner 35445KIT replaces all of them.
What fluid goes in a rebuilt 8L90?
Dexron HP, such as Mobil 1 Synthetic LV ATF HP. Do not refill a rebuilt 8L90 with the original Dexron VI.