4L60-E, 4L65-E and 4L70-E Transmissions units it is common for the plastic forward accumulator piston to wear or crack. causes a loss of fluid, resulting in delayed engagement.
77987-01K:
Piston
D-Ring
PTFE Seal
Steel balls (2)
77998-03K (2PC):
D-Ring
Pinless Accumulator Piston Aluminum
Seal PTFE
Steel Ball .312" dia.
Steel Ball .236" dia.