4L60E 4L65E 4L70E Transmission Sonnax Pinless Forward, 1-2, and 3-4 Accumulator Piston Kit (Includes all 3 accumulators) Material: Aluminum 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 In GM 200-4R, 4L60 and 4L60-series 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