The K1 clutch in Mercedes 722.9 transmissions is applied in third, fourth and fifth gears. The K1 regulator valve controls the apply rate of this clutch. Excess bore wear here permits pressure escape from the circuit, resulting in clutch apply timing problems such as flares and harsh or bump shifts. Reconditioning the bore and installing Sonnax oversized K1 regulator valve 88740-08 returns precise shift control by re-establishing hydraulic integrity in the K1 circuit.
Sonnax valve body layouts provide a detailed overview of individual units making it quick and easy to determine what’s available for the specific valve body you’re working on. See all Sonnax valve body layouts.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.