The B2 clutch in Mercedes 722.9 transmissions is applied in first through fourth gears, and the BR clutch is used during Reverse operation. The B2/BR regulator valve controls the apply rate for these clutches. Bore wear at the B2/BR regulator valve allows pressure loss that affects clutch apply timing, resulting in harsh engagement, delayed Forward and Reverse, flares, and harsh 4-5 shifts. Reconditioning the bore and installing Sonnax oversized B2/BR regulator valve kit 88740-04K renews critical clearances to restore normal Forward and Reverse operation.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.