Improve GM 4L80-E, 4L85-E and TH400 transmission durability with Sonnax heavy duty intermediate clutch outer sprag race 34663HD-02. It’s an ideal upgrade for performance applications where race damage and sprag rollover is common, especially in high-torque vehicles. The Sonnax race is manufactured from case-hardened alloyed steel with softer core and custom designed with an inner diameter a few ten-thousandths of an inch smaller than OE races. This unique combination of features significantly improves sprag element engagement and rollover resistance.

Sonnax 34663HD-02 is the same thickness as the 4L80-E, 4L85-E OE part and .040" thicker than the TH400. It is a direct replacement when used with 4L80-E and 4L85-E direct drums. It can be retrofitted with minimal drum machining to the TH400 roller clutch and sprag-style drums, where the extra race thickness adds to durability and expands clutch stack-up options when using a thinner intermediate clutch backing plate such as Sonnax 34144HD-01.

• Improved material and design guard against sprag failure
• Ideal for all stock and performance applications, regardless of power level
• Direct replacement for 4L80-E, 4L85-E units, easily adapted to TH400