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


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


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

5R55S, 5R55W

Boost Valve Kit
Part No. 56947J-74K

You need this if... View Instructions Find a Distributor

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
  • Drop-in Zip Valve parts install quickly and easily
Learn More About Zip Valve™ Drop-In Repairs
  • Sleeve
  • Inner Boost Valve
  • Outer Boost Valve

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.

Ford 5R55S, 5R55W Valve Body Layout

Ford 5R55S, 5R55W Valve Body Layout
  • 5R55S, 5R55W Boost Valve Kit 56947J-74K
  • 5R55S, 5R55W Boost Valve Kit 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.

5R55S, 5R55W Boost Valve Kit Vacuum Test Locations