6L80, 6L90 (300mm)

Performance Converter Kit
Part No. GM-RK-21

For street/strip and towing applications.

View Instructions

GM 6L80 and 6L90 gas-powered applications that use a full-size torque converter often have engine modifications for increased output, towing heavy loads, or both, which can quickly push the stock single-disc converter clutch past its capacity. To add strength and durability to stock converters, Sonnax offers forged front cover GM-CC-13 and piston plate GM-DA-17P.

For customers with more demanding applications, Sonnax offers performance converter kit GM-RK-21. Employing a forged cover, forged piston and three woven carbon friction elements, builders now have a dampered 300mm multi-plate option that delivers significantly increased clutch capacity and durability. By re-using the OE damper with the Sonnax clutch plates (bonded with OE woven carbon friction material), GM-RK-21 ensures optimal TCC apply and release characteristics, as well as slip rates that match OE continuous slip calibrations. Drivability is excellent. This easy-to-build and cost-effective kit includes clear, concise instructions.

While testing this kit, Sonnax found that the pressure needed to keep this multi-plate TCC slipping at the calibrated rate was much less than the pressure needed in a comparable single-disc converter. Because the Sonnax multi-plate clutch needs less pressure, there is less demand placed on transmission electronics and hydraulics. With the GM-RK-21, it’s easy for the transmission to keep the TCC slip within required slip parameters.

Enhanced design features includes:

  • OE friction material bonded to each clutch plate
  • Forged components assure rigid apply and reaction surfaces
  • Lathe turned feature on mount pads identifies this kit as a multiplate
  • Added clutch capacity reduces required lockup pressure
  • Lower operating pressure reduces demand on transmission electronics and hydraulics
  • Front Cover
  • Clutch plate with external splines
  • Clutch with internal splines
  • Piston
  • Rivets (8) 2 Extra
  • Transmission Unit: 6L80/6L90
  • Core: GM 6L80/6L90 JMBX Converter
  • Dampered: Yes
  • Lockup: Multi-Plate
  • Unit Size: 300mm
  • Clutch Material: Woven Carbon

Where to Buy

  • Existing Customers: Contact your sales representative.
  • New Customers: Fill out the form and a sales representative will contact you.
  • 6L80, 6L90 (300mm) Performance Converter Kit GM-RK-21
  • 6L80, 6L90 (300mm) Performance Converter Kit GM-RK-21 details

Sonnax Performance Converter Kits

Engineered to Deliver Builds that Last

Designed from the ground up to outperform OE and other aftermarket components, Sonnax has you covered with a full line of performance converter kits for gas and diesel vehicles. Offering the widest variety of options in the aftermarket, these innovative kits deliver customized performance and value.

  • Small/Large Diameter
  • Single-Plate/Multi-Plate/Non-Lockup
  • Dampered/Damperless


Choose the right kit for your rebuild!