General Motors
Source-verified model
General Motors 8L90
The RWD automatic transmissions with longitudinal positioning Hydra-Matic 8L90 (M5U) and 8L45 (M5N, M5T) were designed in 2015 for Cadillac CT6 with new engines (3.6 liters) and also suitable for 6-liter engines V8. The design of this modern transmission is similar to 8HP by ZF and has a lot of same "features", like Start-Stop system on at traffic lights, used to save more fuel.
Speeds
8
Type
AT
Drive
RWD/AWD
Max torque
1000
ATF capacity (L)
11,7
ATF change (L)
6
ATF type
Dexron HP
Other and alternative codes of this transmission
8L90
M5U
verified naming
OEM designation
source name
Common problems & symptoms
Problems and symptoms reported for this transmission, compiled from repair sources. Not a complete list.
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Friction Elements Wear Accelerated
Frequent kickdown with controlled lock-up clutch slipping causes rapid friction element wear and contamination.
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Valve Body Contamination
Worn friction elements contaminate valve body, ATF fluid, and filter, impairing hydraulic control.
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ATF Transparency Loss
Loss of ATF clarity indicates contamination from wear debris; signals need for immediate fluid and filter change.
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Lock-Up Clutch Slipping Damage
Controlled slipping of torque converter lock-up clutch under kickdown conditions accelerates overall drivetrain wear.
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Plastic Filter Clogging
Two-layer felt membrane plastic filter clogs from friction debris; requires timely replacement to prevent flow restricti
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ATF Degradation Early
Aggressive driving style and skipping winter warm-up routine accelerate ATF degradation, reducing service interval.
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Pan Debris Accumulation
Pan inspection reveals wear particle accumulation, indicating component wear level and valve body contamination state.
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Cold Start Thermal Stress
Skipping transmission warm-up in winter before driving increases thermal stress and accelerates internal component wear.
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About this transmission
Transmission general data
The RWD automatic transmissions with longitudinal positioning Hydra-Matic 8L90 (M5U) and 8L45 (M5N, M5T) were designed in 2015 for Cadillac CT6 with new engines (3.6 liters) and also suitable for 6-liter engines V8. The design of this modern transmission is similar to 8HP by ZF and has a lot of same "features", like Start-Stop system on at traffic lights, used to save more fuel.
Technical issues and repair guidelines
The transmissions has much higher reserve on components than its German competitor and should operate at least 200-300 thousand kilometers before the first overhaul ( under the condition of well-timed ATF change). In case of frequent “kickdown” usage with a switch-on of controlled slipping of the lock-up clutch, the wear-out of friction elements occurs quite rapidly and contaminates the valve body, fluid and filter. The filter is made of plastic with a two-layer felt membrane and its better to change this part in a timely manner.
The oil and filter should be changed when there are any suspicions related to oil transparency. Such situations may occur after travelling 40 thousand kilometers or 80 thousand kilometers depending on driving style and adherance to the transmission warm-up rule before driving in winter time. Removal of the pan allow specialists to estimate the level of components wear-out and valve body contamination.
Vehicle fitment explorer
Confirmed vehicle applications. Every row is drawn from our source-verified fitment database.
| Make | Model | Year | Drive | Engine |
|---|---|---|---|---|
| Cadillac | ATS | 15-16 | 8 SP RWD | V6 3.6L |
| Cadillac | CT6 | 15-16 | 8 SP 4WD | V6 3.0L |
| Cadillac | CTS | 15-16 | 8 SP RWD | V8 6.2L |
| Cadillac | ESCALADE | 15-16 | 8 SP R/4WD | V8 6.2L |
| Cadillac | ESCALADE ESV | 15-16 | 8 SP R/4WD | V8 6.2L |
| Chevrolet | Camaro | 17-25 | 8 SP RWD | V8 6.2L |
| Chevrolet/GM | CAMARO | 15-16 | 8 SP RWD | V8 6.2L |
| Chevrolet/GM | CORVETTE | 14-16 | 8 SP RWD | V8 6.2L |
| Chevrolet/GM | SIERRA | 14-16 | 8 SP R/4WD | V8 6.2L |
| Chevrolet/GM | SILVERADO | 14-16 | 8 SP R/4WD | V8 5.3L 6.2L |
| Chevrolet/GM | YUKON XL | 06-16 | 8 SP R/4WD | V8 6.0L 6.2L |
Sources & Contribution
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