The 8L90 (and smaller 8L45) is GM's 8-speed automatic. Found in 2015-2018 Silverado, Sierra, Camaro, Corvette, Cadillac. Known for a specific TCC shudder issue. Here's the complete guide.
8L90 basics
- 8-speed automatic
- Years: 2015+ production (early years 2015-2018 had specific issues)
- Applications: Silverado 1500, Sierra 1500, Tahoe, Yukon, Cadillac Escalade, Corvette Stingray/Z51, Camaro SS, CT6
- Torque capacity: ~620 ft-lb stock
- Weight: ~170 lbs
- Co-developed: With Ford (became 10L80 in Ford applications and 10R80 in GM applications)
8L45 basics
- 8-speed automatic (smaller)
- Years: 2016+ production
- Applications: Cadillac ATS, CTS, Camaro V6, smaller GM applications
- Torque capacity: ~430 ft-lb stock
- Weight: ~155 lbs
The famous 8L90 shudder issue
What is the shudder?
At cruising speeds (45-65 mph), the 8L90 develops a noticeable shudder feeling like the trans is "loose" or vibrating.
Root cause
TCC apply piston wear and clutch material breakdown in the torque converter. Affects specific 2015-2018 production years.
How to identify
- Steady shudder at 45-65 mph cruise
- Worse when accelerating mildly
- Disappears at full throttle (TCC disengages)
- Disappears when coasting (TCC slips)
GM's TSB response
GM issued service bulletins for this issue:
- TCM software update (sometimes helps)
- Fluid flush with Mobil 1 LV ATF (sometimes recommended)
- Torque converter replacement (the real fix)
- Trans replacement (warranty cases)
Cost of fixing the shudder
- Software update: free at dealer (during warranty), $100-200 after
- Fluid flush: $200-400
- Torque converter replacement: $1,500-2,500 (parts and labor)
- Trans replacement: $4,000-6,000
When the fix works:
- Software update: helps 30% of cases
- Fluid flush: helps 40% of cases
- TCC replacement: helps 90%+ of cases
8L90 / 8L45 common failures (beyond shudder)
1. Wave plate (similar to 6L80 issue)
The wave plate in the 1-2-3-4 clutch pack distorts. Causes harsh shifts.
Fix: Sonnax billet wave plate during rebuild.
2. Direct clutch wear
HD applications stress the direct clutch.
Fix: HD direct clutch.
3. Valve body wear
Aluminum bore wear over time.
Fix: Bore correction kits if available.
4. Solenoid pack failure
Internal solenoid pack fails at 100K+ miles.
Fix: Solenoid pack replacement.
5. TCC apply piston (the shudder)
Causes the famous shudder.
Fix: Updated TCC apply piston (often part of torque converter replacement).
6. Pump wear
HD pump but still wears.
Fix: Pump rebuild during major service.
8L90 rebuild kit recommendations
Stock daily driver (Silverado 1500 5.3L, Camaro V6)
- Quality master rebuild kit (Transtec gaskets, Alto frictions)
- Sonnax billet wave plate
- HD direct clutch
- Solenoid pack (if 100K+)
- TCC apply piston upgrade
- Stock-replacement HD torque converter
- Total parts cost: $1,200-1,800
- Build cost installed: $4,000-5,500
- Expected life: 100,000+ miles
Tow rig (Silverado 1500 6.2L, Sierra HD package)
- Master kit with Alto Power Pack frictions
- Sonnax billet wave plate
- HD direct clutch with extra plate
- Solenoid pack
- Performance HD torque converter (HD diesel-spec or performance)
- Performance valve body
- Total parts cost: $1,800-2,800
- Build cost installed: $5,500-8,000
- Expected life: 80,000+ miles tow
Performance (built Camaro SS, Corvette Z06)
- Raybestos Stage-1 master kit
- Sonnax billet wave plate
- HD clutch packs with extra plates
- Performance valve body
- Race-spec torque converter
- Custom TCM tune
- Total parts cost: $3,000-5,000
- Build cost installed: $7,500-12,000
- Expected life: Depends on use
8L90 vs 6L80 differences
Gear count
8L90: 8 forward gears
6L80: 6 forward gears
Fuel economy
8L90: 1-2 MPG better than 6L80 (lower cruise RPM)
Acceleration
8L90: Quicker (more gears = better matching)
Torque capacity
8L90: ~620 ft-lb stock
6L80: ~480 ft-lb stock
Cost
8L90: More expensive to rebuild
6L80: Cheaper, more parts availability
Reliability
8L90 (2015-2018): Some issues with shudder
8L90 (2019+): More refined
6L80: Mature design, mostly bugs worked out
8L90 vs 10L80 differences
Gear count
8L90: 8 gears
10L80: 10 gears
Cost
8L90: $4,000-5,500 rebuild
10L80: $5,000-7,000 rebuild
Aftermarket support
8L90: Limited but growing
10L80: Even more limited (newer)
Year-by-year 8L90 notes
2015 8L90
First production. Most issues with shudder. Many TCC replacements.
2016-2017 8L90
Refinements but shudder still common.
2018 8L90
Late-model 8L90. Many shudder cases by this point.
2019+ 8L90
Updated. Less shudder. More refined.
Maintenance recommendations
Fluid service
- 8L90 uses Dexron VI (some early models specified ULV)
- Service every 30-50K miles for tow rigs
- Daily drivers: every 50-75K miles
- "Lifetime fluid" claim is marketing
Cooler upgrade
- Tow applications benefit from external cooler
- Helps reduce overall trans temps under load
TCC monitoring
- Watch for shudder development
- Address early (software update first)
- Plan for TCC replacement if needed at 80-120K miles
Common 8L90 rebuild mistakes
Mistake 1: Ignoring the wave plate
Like the 6L80, the wave plate is a known failure point. Sonnax billet wave plate is mandatory.
Mistake 2: Cheap torque converter
Don't reuse a worn converter. Don't buy cheap converter. The TCC is the most stressed component.
Mistake 3: Skipping solenoid pack at high miles
At 100K+, solenoid pack is approaching end of life. Replace as part of rebuild.
Mistake 4: Wrong fluid
Use Dexron VI. Some early models may have specific ULV requirement — verify for your year.
Mistake 5: TCM update skipped
After rebuild, verify TCM is up to date. Old TCM software can cause shift quality issues.
Brand recommendations
Master rebuild kits
- Alto (Red Eagle, Power Pack)
- Raybestos (Stage-1, GPZ for performance)
- Transtec (gaskets and seals)
- Precision International (mid-tier acceptable)
HD upgrades
- Sonnax (billet wave plate, valve body kits)
- ATI (performance for Camaro/Corvette)
- Goerend (general performance)
Solenoid packs
- ACDelco / GM (OEM equivalent)
- Borg-Warner
- TYC for some applications
Torque converters
- Goerend
- Suncoast Converters
- ATS
- BD Diesel (some applications)
- ATI Performance
Cost summary
8L90 rebuild costs:
- DIY parts only: $1,200-3,500
- Independent shop: $4,000-6,000
- Performance shop: $6,000-12,000
8L45 rebuild costs:
- DIY parts only: $1,000-3,000
- Independent shop: $3,500-5,000
- Performance shop: $5,500-9,000
TCC-only fix (no rebuild):
- New torque converter installed: $1,500-2,500
- Plus fluid service: $200-400
- Total: $1,700-2,900
Reman swap:
- 8L90 quality reman: $3,500-4,500 installed
- 8L45 quality reman: $3,000-4,000 installed
What we sell
Master rebuild kits for 8L90 and 8L45, Sonnax billet wave plates, OEM-spec solenoid packs, performance valve body parts, HD torque converters, and complete shift solutions.
Need 8L90 or 8L45 parts? Shop our 8L90 catalog. Master rebuild kits, Sonnax wave plates, OEM solenoid packs, performance torque converters. Free shipping over $70. Same-day ship in-stock.
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