6L80, 6L90 (300mm), 6L80, 6L90 (JMBX), Multi-Plate Performance Converter

JMBX Performance Converter Kit
Part No. GM-RK-688

Street/Strip applications only. For use with GM 258mm early-style stators only.

View Instructions

A performance torque converter is highly specialized based on the performance characteristics of the specific vehicle. Sonnax has several levels of kits to ensure the best combination of performance and value for each application. These patented, powerhouse kits can be built in a variety of stall speeds, and offer fast, easy assembly with predictable tuning adjustments.

Sonnax JMBX performance converter kit GM-RK-688 for GM 6L80, 6L90 (JMBX) applications delivers the performance characteristics of a high-stall with maximum lockup capacity.

Designed from the ground up to outperform OE and other aftermarket components, other kits that utilize GM 245mm or 265mm core are available.

  • Fits 10.750", 11.062" and 11.500" flexplate bolt patterns
  • Extra-thick piston resists bending and flexing under all extreme applications
  • Heat-treated piston splines hold up under extreme lockup pressure
  • Chromoly steel turbine/impeller hubs plus a fully-machined forged front cover provide superior strength and durability
  • Build in a variety of stall speeds
  • Fast, easy assembly with predictable tuning adjustments

Includes Sonnax base kit [GM-RK-20M].

  • Pilot
  • Turbine Hub
  • Rivets (20)
  • Sprag Cartridge
  • Impeller Hub
  • Front Cover
  • Washer Vespel®
  • O-Ring Fluorocarbon
  • Clutch Plate with Internal Splines, HTE Frictions
  • Clutch Plate with External Splines, HTE Frictions
  • Damperless Piston
  • Thrust Bearing Turbine-side
  • Thrust Bearing Impeller-side
  • Unit Size: 300mm
  • Core: GM 258mm
  • Dampered: No
  • Lockup: Multi-Plate
  • Clutch Material: HTE
  • Transmission Unit: 6L80, 6L90
  • Turbine Hub Input Spline Count: 36

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), 6L80, 6L90 (JMBX), Multi-Plate Performance Converter JMBX Performance Converter Kit GM-RK-688

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!