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Vehicles with a 200-4R, 700-R4, or 4L60-E transmission can experience 1-2 light throttle abrupt or "bang" shifts, especially when using the "093" Corvette or "553" 2nd apply servo pistons. The current industry solution is to make the servo piston apply diameter smaller. This, however, limits the 2-4 band life. This shift problem commonly occurs when the accumulator valve is too large for the application, resulting in too much pressure on the 2-4 band. This valve train has 7 different OEM size variations: B, A, N, M, L, K, and F. They range from the largest valve diameter giving the firmest shift (B) to the smallest valve diameter giving the softest shift (F), respectively. The size variations are clearly stamped with the letter on the aluminum sleeve. Most vehicles, depending upon the transmission/engine combination, can use either the M, L, or K version. However, these are not available unless scavenged from other valve bodies. Sonnax has designed a replacement accumulator valve train assembly the M (.341" valve diameter) 77777M-K. Using the 77777M-K allows you to maintain holding power and proper shift feel. The sleeve is manufactured from high quality aluminum that is designed to prevent excessive wear due to the reciprocating motion of the steel valve. The accumulator valve kit contains three springs of varying spring rates to choose from. Refer to the chart to determine which valve and spring combination best suits the vehicle application.
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