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.
Sonnax oversized 1-2 accumulator valve 84754-57K is made from wear-resistant, hard-coat anodized aluminum to prevent future wear in a refurbished bore. Annular grooves have been added to the valve spool to hydraulically center the valve in the bore for wear resistance.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.