6L80, 6L90

Heavy Duty 4-5-6 Clutch Apply Piston Kit
Part No. 104960-01K

Use with OE-style, 36-tooth frictions & OE steels.

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GM 6L80 and 6L90 transmissions often suffer failure of the 4-5-6 clutch assembly due to OE design shortcomings. Insufficient clutch piston-to-plate apply surface area causes clutch plate failure, especially when apply pressures exceed OE specifications. The other problem is flexing and bowing of the backing plate (coning), which is a primary source of clutch failure.

The heavy duty Sonnax 4-5-6 clutch apply piston kit 104960-01K addresses these weak areas in two ways:

  1. A modified OE clutch apply piston and piston dam are used in conjunction with a specially-designed Sonnax piston apply ring.
  2. A more rigid backing plate.

The Sonnax apply ring increases surface area between the apply piston and OE waved clutch plate, resulting in more even distribution of apply force to clutch plates. The Sonnax backing plate minimizes flexing/bowing when clutch is applied, drastically reducing the likelihood of clutch plate distortion.

  • Solid backing plate design outperforms OE and aftermarket plates
  • Increased apply ring surface area improves clutch apply
  • Reduces heat buildup
  • Use with stock clutches and OE waved plate

OEM frictions are about .063" thick, and OEM steels are about .086" thick. Clutch capacity is 6 frictions for the 6L80 and 7 frictions for the 6L90.

  • Apply Piston
  • Apply Ring
  • Piston Dam
  • Backing Plate

  • 6L80, 6L90 Heavy Duty 4-5-6 Clutch Apply Piston Kit 104960-01K
  • 6L80, 6L90 Heavy Duty 4-5-6 Clutch Apply Piston Kit 104960-01K details


GM 6L80 Series Transmission Upgrades & Repairs
6L80 & 6L90 Upgrade Options for the 4-5-6 Clutch