298mm LU (TH250C, TH350C, 200-4R, 4L60 & E), 4L60-E (298mm), Single-Plate Performance Converter

298mm Performance Converter Kit
Part No. GM-RK-18

View Instructions

The GM 4L60-E transmission used the 298mm converter starting in 1992 and as late as 2004 in the Corvette. The large diameter and weight of this converter rob the drivetrain of acceleration power and throttle response. Sonnax 298mm performance converter kit GM-RK-18 adapts a GM245mm core for use in 4L60-E (298mm) applications, allowing converter builders to assemble high-performance 4L60-E converters with a variety of stall speed options.

The diameter of the finshed converter using the GM-RK-18 is 1.600" (40mm) smaller, which improves acceleration. The new robust 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 other GM applications.

The GM-RK-18 kit utilizes the OE GM 258mm damper assembly to isolate engine and road vibration and to protect the transmission downstream. Many other aftermarket performance converter kits offer pistons without dampers, which will compromise ride quality for street use and severely reduce 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 complete GM 258mm piston/damper.

The GM-RK-18 kit is designed to fit either Sonnax stator GM-ST-082 and GM-ST-086 along with a sprag cartridge GM-CS-3 that fits the 4L60-E stator shaft spline. Instructions for cutting and welding the 245mm turbine to accept the turbine hub are included with the kit.

  • Improved acceleration and throttle response
  • Adapts the popular GM 245mm converter core
  • Includes heavy duty front cover
  • Fits 9.674" (245mm), 11.062" (281mm) and 11.500" (292mm) flexplate bolt patterns
  • Weld-on cover pilots for 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
  • 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.
  • 298mm LU (TH250C, TH350C, 200-4R, 4L60 & E), 4L60-E (298mm), Single-Plate Performance Converter 298mm Performance Converter Kit GM-RK-18

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!