6L80 vs 6L90: GM HD 6-Speed Comparison

The 6L80 and 6L90 are GM's HD 6-speed automatics. They look identical but the 6L90 is significantly stronger. Here's the comparison.

Quick overview

6L80 (2006-present):

  • 6-speed automatic
  • ~470 ft-lb stock capacity
  • Found in: 1500-series trucks, Tahoe/Yukon, Camaro
  • Read our best 6L80 rebuild kit

6L90 (2007-present):

  • HD 6-speed automatic
  • ~580 ft-lb stock capacity
  • Found in: 2500/3500 HD trucks (gas), Suburban HD, Express vans

Read our 4L80E vs 6L80 comparison

Gear ratios

Same for both:

  • 1st: 4.03
  • 2nd: 2.36
  • 3rd: 1.53
  • 4th: 1.15
  • 5th: 0.85
  • 6th: 0.67

Result: identical gearing, different strength

Strength comparison

Stock:

  • 6L80: ~470 ft-lb
  • 6L90: ~580 ft-lb

With HD upgrades:

  • 6L80: 650+ ft-lb (Sonnax billet)
  • 6L90: 750+ ft-lb (Sonnax billet)

Read our 6L80 wave plate replacement

Key differences

Internal hard parts:

  • 6L90 has stronger planetary gear set
  • 6L90 has updated input drum
  • 6L90 has additional friction in some clutch packs

Pump:

  • 6L90 has slightly higher capacity pump
  • Better lube circuit for HD use

Case:

  • 6L90 has reinforced areas
  • Same exterior dimensions

Read our 6L80 input drum failure

Applications

6L80:

  • 2007-2014 Silverado/Sierra 1500
  • Tahoe/Yukon standard
  • Camaro Z28, some Corvette
  • Read our 4L60E vs 6L80

6L90:

  • 2007-2013 Silverado/Sierra 2500HD/3500HD (gas)
  • Suburban HD
  • Express vans
  • HD passenger applications

Parts interchange

Mostly interchange:

Different (don't swap):

  • Hard parts (planetary, drums)
  • Some friction packs
  • Specific HD components

Common failures

Same failure modes:

6L90 less prone:

  • Stronger internals
  • Heavy-duty parts last longer
  • Still benefits from HD upgrades

Read our 6L80 common failure codes

Rebuild costs

6L80:

6L90:

  • DIY: $1,200-2,000
  • Shop: $2,800-5,000
  • Slightly higher due to HD parts

Identification

By RPO code:

  • 6L80: MYC
  • 6L90: MYD

By application:

  • 1500-series gas truck: 6L80
  • 2500/3500 gas truck: 6L90
  • HD applications: 6L90

Read our how to identify your transmission

When to choose which

6L80 sufficient for:

  • 1500-series truck
  • Daily driver use
  • Light tow (under 8,000 lb)
  • Performance with HD upgrades

6L90 better for:

  • HD truck
  • Regular tow over 8,000 lb
  • Higher capacity needed
  • Long-term HD ownership

Read our 4L80E vs 6L80 for older alternative

HD upgrade paths

6L80 HD:

  • Sonnax billet input drum
  • Sonnax billet wave plate
  • HD clutch packs
  • Updated TCC PWM
  • Total: $400-800 extra in rebuild
  • Read our Sonnax explained

6L90 HD:

  • Same upgrades available
  • Starting point is stronger
  • Total: $400-800 extra in rebuild
  • Result: bulletproof for HD use

Operating costs

Both:

Common confusion

"Is my 1500 truck a 6L80 or 6L90?"

  • Always 6L80
  • 6L90 only in HD trucks

"Can I swap 6L80 for 6L90?"

  • Different mounting in some applications
  • Verify driveline
  • Generally same family

"Do 6L80 parts fit 6L90?"

  • Many interchange
  • Hard parts often don't
  • Verify specifically

Read our transmission parts buying guide

Year-by-year notes

2007-2010 6L80:

  • Earliest failures
  • Updates rolling out

2011-2014 6L80:

  • Updated TCC
  • Better reliability
  • HD aftermarket available

2015+ 6L80:

  • Best 6L80 version
  • Then replaced by 8L90 in 1500
  • Read our 6L80 vs 8L90

6L90 throughout production:

  • More consistent
  • Less variation year-to-year
  • HD focused

After rebuild

Adapt learn:

Service intervals (HD):

Need 6L80 or 6L90 parts? Shop our 6L80 catalog. Both rebuild kits, Sonnax billet upgrades, complete parts. Free shipping over $70.

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