Gearbox GM 8L90

The General Motors 8L90 (M5U) 8-speed automatic transmission has been produced in the United States since 2014 and is installed in popular models such as the Chevrolet Corvette, Camaro, Tahoe, and Cadillac Escalade. It is designed for rear- and all-wheel drive vehicles with particularly powerful engines.

Specifications

Type	automatic transmission
Number of gears	8
Type of drive	rear / all wheel
Engine volume, l	up to 6.2
Torque output, Nm	up to 860
Recommended oil	Dexron HP
Oil capacity, liter	10.8
Partial replacement, liter	7.0
Maintenance	every 60 000 km
Gearbox lifespan, km	~250 000 km
Weight, kg	95

Gear ratios GM 8L90

Using the 2017 Chevrolet Corvette Z06 with a 6.2-liter engine as an example:

Main	2.41
1st	4.560
2nd	2.971
3rd	2.075
4th	1.688
5th	1.270
6th	1.000
7th	0.846
8th	0.652
Reverse	3.817

Using

The transmission was installed on:

• Cadillac ATS I (A1SL) in 2016 – 2019;
• Cadillac CTS III (A1LL) in 2016 – 2019;
• Cadillac CT6 I (O1SL) in 2016 – 2020;
• Cadillac Escalade 4 (GMTK2XL) in 2014 – 2019;
• Chevrolet Camaro 6 (A1XC) in 2015 – …;
• Chevrolet Corvette C7 (Y1BC) in 2014 – 2019;
• Chevrolet Silverado 3 (GMTK2RC) in 2015 – 2019;
• Chevrolet Silverado 4 (GMT1RC) in 2018 – …;
• Chevrolet Suburban 11 (GMTK2YC) in 2015 – 2019;
• Chevrolet Tahoe 4 (GMTK2UC) in 2015 – 2020;
• GMC Sierra 4 (GMTK2RG) in 2015 – 2019;
• GMC Sierra 5 (GMT1RG) in 2018 – …;
• GMC Yukon 4 (GMTK2UG) in 2015 – 2019;
• GMC Yukon XL 4 (GMTK2YG) in 2015 – 2019.

Disadvantages of the GM 8L90 gearbox

• A known issue with this transmission is jolting and vibration during gear shifts;
• There was even a recall campaign, but the manufacturer limited it to an oil change;
• The only way to completely eliminate transmission vibrations is to replace the torque converter;
• Furthermore, unreliable solenoids caused a lot of trouble during the first two years of production;
• The C4 piston and the oil pump drive chain are also considered weak points of the automatic transmission.