Buick TH350 | Chevy TH350 | Powerglide | Powerglide, TH350, TH400 (258mm) Performance Converter | TH400 (3L80), AT-540

258mm Performance Converter Kit
Part No. GM-RK-308

View Instructions

Sonnax 258mm performance converter kit GM-RK-308 for GM Powerglide, TH350 and TH400 258mm applications allows builders to assemble a high performance converter with minimal effort. With the readily available GM 258mm converter cores, a variety of stall speeds can be built using different stator and impeller combinations.

Fully machined cover with bushing installed
Unit-specific design for hassle-free installation
Oil flow grooves and holes increase fluid flow to keep converters running cooler
Turbine hub features a larger flanged diameter to increase the strength rigidity of the turbine
Clear, detailed instructions

Note

Pilot kit not included.

This 258mm kit will not fit GM AT-540 units. View Sonnax 245mm converter upgrades available for this unit.

Contents

Thrust Bearing
Flanged Impeller Hub
30-Tooth Turbine Hub
Front Cover, 10-3/4" Single Bolt Patter
Front Cover Bushing Installed

Specs

Unit Size: 258mm
Core: GM 258mm
Dampered: No
Lockup: No
Transmission Unit: TH350, TH400, Powerglide
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.

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.