In GM 4L60-E, 4L65-E and 4L70-E units it is common for the plastic forward accumulator piston to wear or crack. This causes a loss of fluid, resulting in delayed engagement, slips, burnt clutches and/or bands. Repeated reciprocation of the accumulator piston causes the piston pin bore to wear, while fluid loss through the piston pin bore or cracks causes forward clutch to slip. Sonnax pinless forward accumulator piston kit 77987-01K eliminates these problems.

• Dual seals stabilize and completely seal the bore, providing a tight seal even after thousands of cycles
• Pinless design eliminates the possibility of pin leakage, and the additional length stabilizes the piston to prevent piston cocking
• Includes steel balls for plugging existing pin bore in valve body
• Drop-in Zip Valve™ parts install quickly and easily