Symptoms:

  • Cracked pistons
  • Burnt clutches
  • Burnt bands
  • Forward slip
  • Delayed engagement
  • Aluminum 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.

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

Forward Accumulator Piston
Part No. 74927-AP

OE Part No. 8686017 or 24200126

Find a Distributor

In 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.

Learn More About Zip Valve™ Drop-In Repairs

Sonnax valve body layouts provide a detailed overview of individual units making it quick and easy to determine what’s available for the specific valve body you’re working on. See all Sonnax valve body layouts.

GM 4L60-E, 4L65, 4L70-E Valve Body Layout

GM 4L60-E, 4L65, 4L70-E Valve Body Layout
  • 4L60-E, 4L65-E, 4L70-E Forward Accumulator Piston 74927-AP
  • 4L60-E, 4L65-E, 4L70-E Forward Accumulator Piston 74927-AP