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  • 3-4 Harsh
  • Low Reverse pressure
  • No 5th
  • 2-3 Harsh
  • 4-5 Harsh
  • C2 Clutch burned
  • B1 Clutch burned
  • B2 Clutch burned
  • High line pressure in Reverse


Oscillation of the shift pressure control valve within its sleeve causes wear, which will allow Drive or Reverse pressure being routed to the B2, B1 or C2 clutch to exhaust or cross leak. This will result in shift complaints and burnt clutches.


Restore proper hydraulic control by replacing worn parts with the improved, drop-in Sonnax kit.

55-50SN, 55-51SN

Shift Pressure Control Valve Kit
Part No. 59947-38K

Also fits Aisin AW 55-51SN, AF 23/33 and RE5F22A units.

You need this if... View Instructions

The shift pressure control valve in Aisin AW 55-50SN 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. The drop-in 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.

  • Valve is hardcoat anodized to reduce wear
  • Annular grooves on the valve hydraulically center it in the bore to prevent sleeve wear
  • Valve
  • Sleeve

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.

Aisin AW 55-50SN Valve Body Layout

Aw55 50sn vbl thumb

September 30, 2005

Anatomy of a Transmission: Oil Flow in the Pump-PR-Converter-Cooler Lube Circuits

Gregg Nader

Topics: Diagnostics And Theory Transmission

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  • 59947 38k combo
  • 59947 38k

You need this if...

A vacuum test at the port indicated fails to hold at least 18 in-Hg, or if visual wear is detected in the sleeve.

  • 59947 38k test