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