March 21, 2013
To help control the 2nd clutch apply pressure and shift feel in the GM 4T65-E, a 1-2 accumulator piston and accumulator valve regulating fluid pressure are used. The 1-2 accumulator valve regulates line pressure using torque signal influence and directs 1-2 accumulator pressure to the spring side of the piston, controlling the 2nd clutch apply. Wear at the bore or valve can allow torque signal, 1-2 accumulator or line pressures to exhaust, resulting in various 1-2 shift complaints.
Recondition the bore and install Sonnax oversized 102 accumulator valve 84754-57K to restore hydraulic integrity.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.