6L80 and 6L90 share the same case and most internals. The 6L90 is the HD version. Here is what is actually different and what parts swap.
External identification
6L80 (2006-2014):
- 17-bolt pan
- 6-speed automatic
- ~440 ft-lb input rating
- Used in Camaro SS, Silverado 1500, Tahoe
6L90 (2007-2017):
- Same 17-bolt pan
- 6-speed automatic
- ~590 ft-lb input rating
- Used in Silverado 2500/3500, Express HD, Suburban
What is HD about the 6L90
Wider clutches:
- 6L80: 5-disc 1-2-3-4 clutch
- 6L90: 6-disc 1-2-3-4 clutch
- ~30% more clamp force
HD planetary:
- 6L80: stamped carriers
- 6L90: forged carriers
- Higher torque rating
HD output shaft:
- 6L80: 28-spline
- 6L90: 32-spline
- Different driveshaft / yoke
What parts interchange
Same between both:
- Pan and gasket
- Filter
- Valve body (most years)
- Solenoid pack
- Pump assembly
- Most seals and bushings
Different:
- Clutches (count discs)
- Planetary set
- Output shaft and yoke
- Some bell housing bolt patterns
Upgrading 6L80 with 6L90 parts
Worth doing during rebuild:
- 6L90 clutch packs (more frictions)
- HD planetary
- HD line pressure tune
- Adds ~100-150 ft-lb capacity
- $400-$700 extra over basic rebuild
Not bolt-in:
- Output shaft (different yoke)
- Some bell housings (Vortec vs LS rear)
When to choose 6L90 over 6L80
6L90 required if:
- Towing 8,000+ lbs regularly
- 3/4-ton or 1-ton truck
- Heavy fleet/work use
- Tuned 6.0L or 6.2L with sustained load
6L80 fine if:
- Daily driver / commuter
- 1/2-ton truck
- Stock tune
- Light occasional towing
Cost
6L80 rebuild:
- Parts: $400-$800
- Labor: $1,800-$2,800
- Total: $2,200-$3,600
6L90 rebuild:
- Parts: $500-$900
- Labor: $1,800-$2,800
- Total: $2,300-$3,700
6L80 with HD 6L90 parts:
- Parts: $700-$1,200
- Labor: $1,800-$2,800
- Total: $2,500-$4,000
Need 6L80, 6L90, or HD upgrade parts? Shop our 6L80/6L90 catalog. HD clutches, planetary sets, complete rebuild kits. Free shipping over $70.
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