Product Review

SmartShell Heavy Duty Reaction Shell Kit

Stripped or cracked shells in GM 4L60, 4L60-E, 4L65-E and 4L70-E units are a common problem, but strengthening the shell alone does nothing to address the equally common problem of a failed rear planet captured bearing. The Sonnax SmartShell 77749-02K is a heavy duty reaction shell kit designed to prevent damage to the rear planetary assembly as well as provide a reinforced shell.

In the OE sun gear shell, the thrust load passes from the shell through the sun gear, then overloads the small captured planetary bearing. To protect this bearing, Sonnax took the smart approach and replaced the OE black plastic washer with a large thrust bearing and roller clutch race. This re-routes the thrust load directly to the carrier, completely bypassing the delicate bearing.

The SmartShell avoids the substantially increased weight found in other aftermarket shells. The Sonnax approach to improving the shell includes reinforcing the hub area with an laser beam welded collar. A final machining process after welding ensures precision alignment. The SmartShell splines undergo an advanced machining and heat-treating process, and the lugs which engage the drum are heat treated as well to avoid flaring.