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 clutch rides). Sonnax offers a hardened steel sleeve that reinforces the input drum to prevent this failure. OE aluminum overrun pistons must be machined when using this input drum reinforcement kit 77733-02K.

• Sleeve made from hardened chromoly steel
• Can be installed in early- and late-model units*
• Sleeve design will not block clutch feed oil