200-4R 4L60 4L60E 4L65E 4L70E Transmission Enhanced Performance Accumulator Spring Sonnax enhanced performance accumulator spring 77704S provides firmer 1-2 shifts for the enthusiast that appreciates quick, positive shift feel in GM 200-4R, 4L60 and 4L60-E series units. The Sonnax spring design provides performance shift feel, but does not reduce accumulator piston travel. This allows for a firmer - but still cushioned - shift that minimizes shock to the band and shafts. The Sonnax spring achieves the same effect as the common shop practice of replacing the OE 1-2 accumulator spring with the THM 350 direct accumulator piston spring. The Sonnax spring also may be used as a replacement for the THM 350 direct accumulator piston spring.