Check the listing for details. Sonnax 74927-AP Forward Accumulator Piston Aluminum fits 4L60E 4L65E 4L70-E. Condition: New. Listed at 13.95 USD. 4L60-E, 4L65-E, 4L70-E Transmission Forward Accumulator Piston Part No. 74927-AP OE Part No. 8686017 or 24200126In GM 4L60-E, 4L65-E and 4L70-E units, it is common for the plastic Forward accumulator piston to wear or crack and older aluminum piston bores to wear from repeated reciprocation. This causes a loss of fluid, resulting in delayed engagement, slips, burnt clutches and/or bands. Sonnax aluminum Forward accumulator piston 74927-AP eliminates the cracking problem and restores hydraulic integrity at the pin bore. The drop-in Zip Valve™ part installs quickly and easily. Symptoms: Cracked pistonsBurnt clutchesBurnt bandsForward slipDelayed engagementAluminum pistons wear at the pin bore Cause: Wear at the piston pin bore due to repeated reciprocation and/or cracks in the plastic accumulator piston. Correction: Sonnax drop-in, aluminum forward accumulator piston is a direct replacement for the OE plastic piston and restores sealing integrity at the pin bore.