September 30, 2005
The shift pressure control valve in Aisin AW 55-50SN and 55-51SN units is biased by spring force and shift control (SLS) fluid pressure. This valve regulates Drive and Reverse fluid pressure to control the apply of the second clutch (B2), the second coast clutch (B1) or the direct clutch (C2). The constant oscillation of the valve wears the cast aluminum sleeve, allowing Drive and Reverse fluid pressure to leak and cause shift complaints and burnt clutches. Sonnax shift pressure control valve kit 59947-38K uses upgraded materials and annular grooves on the valve to correct the problem and prevent future wear.
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Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.