• Poor shift quality
  • Burnt clutches & bands


Wear at the piston pin bore due to repeated reciprocation.


The Sonnax patented pinless design with dual seals stabilizes the piston in the bore and provides improved sealing characteristics. Use of the Sonnax part eliminates the need for the pins.

200-4R, 4L60, 4L60-E, 4L65-E, 4L70-E

Pinless Accumulator Piston Kit
Part No. 77998-03K

In 200-4R applications, this kit can only be used in the 3-4 accumulator location.

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In listed GM units it is common to have poor shift quality, burnt bands or clutches due to accumulator piston wear. Repeated reciprocation of the accumulator piston causes wear at the piston pin bore interface. After this wear reaches a critical point, fluid loss through the piston pin bore cannot be compensated due to lack of pump volume. In addition, the piston can get cocked and gall the accumulator bore due to the pin bore wear or the spring bottoming out. To prevent these conditions in the 1-2 or 3-4 accumulator bores, Sonnax offers pinless accumulator piston kit 77998-03K.

  • Pinless design eliminates the possibility of pin bore leakage and the additional length stabilizes the piston to prevent piston cocking
  • Dual seals stabilize and completely seal the bore and provide a tight seal even after thousands of cycles
  • Steel balls plug existing pin bore in case or cover
  • D-Ring Viton®
  • Pinless Accumulator Piston Aluminum
  • Seal PTFE
  • Steel Ball .312" dia.
  • Steel Ball .236" dia.

June 06, 2018

All Over the Map: Attacking 4L60/E Burnt 3-4 Clutches with Confidence

Brian Wing

Topics: Shop Practices Transmission GM 4L70-E Transmission 4L60-E Transmission 4L65-E Transmission 4L60 Transmission

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  • 77998 03k combo
  • 77998 03k