280mm LU (4L60-E) “VJCX”, 300mm (4L60-E), 4L60-E (300mm), Single-Plate Performance Converter

300mm Performance Converter Kit
Part No. GM-RK-17

View Instructions

Late GM 4L60-E transmissions use a 300mm converter. The large diameter and weight of this converter rob the drivetrain of acceleration power and throttle response. The Sonnax 300mm performance converter kit GM-RK-17 adapts a GM 245mm core for use in GM 4L60-E (300mm) applications, allowing converter builders to assemble high-performance GM 4L60-E converters with a variety of stall speed options. The diameter of the finished converter using the GM-RK-17 is 1.600" (40mm) smaller, which improves acceleration.

The robust Sonnax forged cover has additional material on the flexplate mounting pads and rim to reduce cover flexing and ballooning during hard acceleration. This cover also incorporates universal features: three different flexplate bolt hole patterns and a weld-on pilot for use with other GM applications.

The GM-RK-17 kit utilizes the OE GM 258mm damper assembly to isolate engine and road vibration and to protect the transmission parts downstream. Many other aftermarket performance converter kits offer pistons without dampers, which will compromise ride quality for street use and severely reduce the transmission and converter life. Two damper assembly options are available with this performance converter kit: forged piston GM-DA-6P assembled with a used GM 258mm damper assembly, or a salvaged OE 258mm converter piston/damper.

The performance converter kit GM-RK-17 is designed to fit either Sonnax stator GM-ST-082 or GM-ST-086, along with a sprag cartridge GM-CS-3 that fits the GM 4L60-E stator shaft spline. Instructions are provided to cut and weld the 245mm turbine to accept the turbine hub.

  • Improved acceleration and throttle response
  • Adapts the popular GM 245mm convertercore
  • Includes heavy duty front cover
  • Fits 9.674" (245mm), 11.062" (281mm) and 11.500" (292mm) flexplate bolt patterns
  • Weld-on pilot adapts to many applications
  • Chromoly steel turbine and impeller hubs

Required Piston Damper Assembly Parts



  • GM 258mm Piston/Damper Assembly

Required Stator Assembly Parts

Required OE Core Parts

  • GM 245mm Impeller
  • GM 245mm Turbine (requires machining)

Optional Assembly Parts

  • B78 Hex Head Screw (100/bag)

This kit must be completed with the additional required Sonnax or OE parts listed. Some machining is required.

  • Pilot
  • Front Cover
  • Thrust Bearing
  • Thrust Washer
  • O-Ring
  • Turbine Hub
  • Shim
  • Impeller Hub
  • Unit Size: 10"
  • Core: GM 245mm
  • Dampered: Yes
  • Lockup: Single-Plate
  • Transmission Unit: 4L60-E
  • Turbine Hub Input Spline Count: 30

Where to Buy

  • Existing Customers: Contact your sales representative.
  • New Customers: Fill out the form and a sales representative will contact you.
  • 280mm LU (4L60-E) “VJCX”, 300mm (4L60-E), 4L60-E (300mm), Single-Plate Performance Converter 300mm Performance Converter Kit GM-RK-17

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!