8-Speed Automatic Transmission Assembly for 2020-2022 Chevrolet & GMC

A quick look at your own vehicle makes sure the right transmission shows up:

• Verify RPO code MQE on the Service Parts Identification label (QR code on driver's side B-pillar door jamb or sticker inside glove box).
• Confirm the vehicle is a 4x4 (4WD) model.
• Confirm the vehicle has a 5.3L V8 engine (RPO L84 or L82).

What the install really takes — plan and budget with confidence:

Special tools this job needs:

• Transmission jack
• Transfer case jack
• GM-compatible dealer-level scan tool (GM MDI / MDI2 / GDS2) with active SPS2 subscription
• Professional cooler line flushing machine
• Fluid fill adapter tool (DT-51190)

Budget for these consumables at install:

• Mobil 1 Synthetic LV ATF HP (Blue Label) fluid
• New OEM transmission filter (GM Part Number 24295812 / ACDelco TF922)
• New pan gasket
• Torque converter seal (front pump seal)
• Turbine shaft O-ring seal
• Transmission cooler flush agent

What your vehicle’s computers will need after the swap:

What’s involved: Solenoid Valve Characterization (MCVM) and Transmission Service Fast Learn

The GM 8L90 transmission uses highly precise variable force solenoids (VFS). You must document the Transmission Unique Number (TUN) from the replacement transmission's case before installing it. Once installed, you must connect a GM-compatible scan tool with an active GM SPS2 subscription, enter the vehicle's VIN, select 'Transmission Control Module - MCVM Operations,' and enter the new transmission's TUN. After programming, a 'Transmission Service Fast Learn' procedure must be performed with a scan tool to calibrate clutch apply pressures.

Pro tips for a smooth first start-up — hand them to whoever does the install:

• Torque Converter Seating: The converter must drop down past three distinct steps (or 'clicks') as it engages the splines and pump flats. Measure the distance from the bellhousing face to the torque converter mounting pads; it should be recessed by at least 1 inch. If it is not fully seated, bolting the transmission to the engine will crack the front pump rotor, instantly destroying the transmission upon startup.
• Thermal Bypass Valve (TBV) and Fluid Level Check: The 8L90 uses an external thermal bypass valve in the cooler lines that remains closed until the transmission fluid reaches 194°F (90°C). To get an accurate fluid level check, you must drive or run the vehicle until the transmission fluid temperature exceeds 194°F to open the bypass valve and fill the cooler lines. Then, let the fluid cool back down to the official level-check window of 95°F to 113°F (35°C to 45°C), start the engine, and remove the level check plug on the bottom of the pan.
• Bellhousing Dowel Pins: Ensure both alignment dowel pins are present and correctly installed in the engine block, not the transmission bellhousing, before installation. Misalignment from missing dowels will destroy the front pump bushing and seal.

Easy to get right once you know them:

• Using the Wrong Fluid: Using standard Dexron VI or generic multi-vehicle ATF instead of the required Mobil 1 Synthetic LV ATF HP (Blue Label).
• Skipping the TUN Programming: Assuming the transmission is 'plug and play' without programming the new transmission's TUN into the vehicle's TCM.
• Forcing the Bellhousing Bolts: Using the bellhousing bolts to 'draw' the transmission tight to the engine block when the torque converter is not fully seated, which cracks the oil pump housing.
• Reusing a Contaminated Cooler: Failing to thoroughly clean or replace the thermal bypass valve and auxiliary cooler after a catastrophic internal failure, which washes old debris into the new transmission.

Not issues with the units on this page — the manufacturer documented these for every transmission of this family, wherever you buy one. Handy for your installer: