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  • Burnt Forward clutch
  • Delayed engagement


A worn forward accumulator piston pin bore.


This oversized replacement accumulator pin restores the proper fit between the piston and the bore and allows re-use of the original aluminum piston.

4L60-E, 4L65-E, 4L70-E

Oversized Accumulator Pin
Part No. 77754-01K

Package Quantity: 4

View Instructions

A common condition in 4L60-E transmissions is a burned forward clutch or delayed engagement. A worn forward accumulator piston pin bore is frequently the source of this condition. The aluminum piston continuously oscillates on a hardened steel pin, which can cause wear resulting in forward clutch oil exhausting. This oil loss reduces accumulator action and decreases the forward clutch apply pressure. The Sonnax replacement oversized accumulator pin 77754-01K eliminates this problem.

  • Oversized accumulator pin restores the proper fit between the piston bore and pin.
  • Pin is made from hardened steel and fits more securely in the valve body bore, preventing oil from exhausting through the valve body.
  • Allows the rebuilder to re-use the original piston while providing a more durable, less expensive solution.
  • Starter kit 77754-02K contains 10 pins plus one reamer.
  • 77754 01k combo
  • 77754 01k