Sonnax SmartShell® 

Heavy Duty Reaction Shell Kit

In GM 4L60, 4L60-E, 4L65-E and 4L70-E units, bulky aftermarket shells always fall short when splines continue to strip and the shells break under stress. 

A chronic problem with both OE and thicker aftermarket shells is failure of the rear planetary bearing. 

From daily jobs to extreme builds, the Sonnax SmartShell heavy-duty reaction shell kit 77749-02K is the only way to prevent shell failure AND protect the bearing.

The SmartShell avoids the weight found in traditional, heavy-duty aftermarket shells thanks to a unique combination of improved design and manufacturing for a super strength shell 

that's only slightly bulkier than OE. 

To prevent thrust loads from overwhelming the captured planetary bearing, the SmartShell features a larger bearing and custom roller clutch race. 

These parts re-route thrust loads through the carrier, completely bypassing the delicate bearing.

• Stops spline stripping
• Prevents hub breakage
• Eliminates planetary bearing failure