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  • Burnt clutches
  • Delayed engagement
  • Erratic line pressure
  • Low line rise
  • Low Reverse boost
  • No Reverse
  • Poor fuel economy
  • Poor shift quality
  • Reverse slip
  • Soft shifts


OE boost sleeve deterioration allows pressure loss that leads to driveability concerns.


Recover hydraulic control and renew shift performance by installing Sonnax boost valve kit.

5R55S, 5R55W

Boost Valve Kit
Part No. 56947J-74K

You need this if... View Instructions

Ford vehicles equipped with 5R55W and 5R55S transmissions frequently exhibit problems such as poor line rise, erratic line pressure, delayed engagement, no Reverse, poor shift quality and burnt clutches. These troubles can often be traced to wear in the OE boost sleeve, which allows pressure escape that causes driveability concerns. Installing Sonnax boost valve kit 56947J-74K eliminates pressure loss and revives line rise and shift quality in all ranges.

  • Sleeve manufactured from highly wear-resistant aluminum
  • Hardcoat anodized aluminum valves combat premature wear
  • Sleeve
  • Inner Boost Valve
  • Outer Boost Valve
  • 56947j 74k combo
  • 56947j 74k

You need this if...

Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.

  • 56947j 74k test