Sonnax 77733-51K Input Drum Reinforcement Kit for GM Automatic Transmission Assembly - 4L60 4L60E 4L65E 4L70E

The Sonnax 77733-51K Input Drum Reinforcement Kit is designed to prevent common input drum failures in GM 4L60, 4L60-E, 4L65-E, and 4L70-E automatic transmissions. These transmissions are known to crack and strip out splines where the input shaft is pressed into the drum, particularly in the overrun piston area. This comprehensive kit provides a durable solution to extend transmission life and reliability.

Kit Includes:

• High-strength chromoly steel reinforcement sleeve
• Custom manufactured overrun piston
• Overrun piston inner seal
• Overrun piston outer seal

Key Features:

• Hardened chromoly steel sleeve reinforces the input drum to prevent cracking and spline damage
• Custom overrun piston designed specifically for use with 1997-later stamped steel forward pistons
• Universal design fits both early and late-model transmission units
• Sleeve design will not block clutch feed oil passages
• No machining required for installation
• Eliminates the need for OE cast aluminum forward pistons or aftermarket billet forward pistons

Important Compatibility Note: This kit must be used with a 1997-later stamped steel bonded rubber seal forward piston. It cannot be used with 1996-earlier cast aluminum forward pistons or Sonnax billet forward pistons. Input drum is not included.

Professional-grade solution from Sonnax, a trusted name in transmission repair and performance components.