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 is a heavy duty reaction shell kit designed to prevent damage to the rear planetary assembly as well as provide a reinforced shell.
Protecting the Planetary Bearing
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.
Strengthening the Shell
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.
The GM 4L60, 4L60-E, 4L65-E and 4L70-E input drum assembly is known to crack where the input shaft is pressed into it (where the overrun piston rides). Sonnax offers a hardened steel sleeve that reinforces the input drum to prevent this failure. Sonnax input drum reinforcement kit includes a custom manufactured overrun piston that is designed to be used only with a stamped steel forward piston, eliminating the need to use OE cast forward pistons or aftermarket billet forward pistons.
- Includes a custom manufactured overrun piston
- Compatible with stamped steel forward pistons
- Can be installed in early- and late-model units
- Sleeve made from hardened chromoly steel
- Sleeve design will not block clutch feed oil
This kit must be used with a ’97-later stamped steel forward piston, it cannot be used with '96-earlier aluminum forward piston