• Soft shifts
  • Poor shift quality
  • Reverse shudder
  • Direct clutch failure
  • Low line rise


Excess boost sleeve wear prevents proper line rise.


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


This kit does not recalibrate shift timing or allow gas and diesel valve body interchange.


Boost Valve Kit
Part No. 36946-03K

Diesel ratio, factory style.

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

Heavy-duty vehicles with Ford C6 transmissions often display poor line rise, which results in erratic shift timing, Reverse shudder or direct clutch failure. This can be caused by excess wear at the inside diameter of the boost sleeve. This wear allows oil to leak past the boost valve to exhaust, resulting in poor or no line rise. Recover the hydraulic integrity of the boost circuit and restore proper line rise by installing Sonnax diesel-ratio boost valve kit 36946-03K.

  • Diesel-ratio kit restores OE boost pressure
  • Sleeve manufactured from highly wear-resistant aluminum
  • Hardcoat anodized aluminum valve combats premature wear
  • Drop-in Zip Valve parts install quickly and easily
Learn More About Zip Valve™ Drop-In Repairs

A number of boost valve kits are available for this unit:

  • Normal line pressure boost (gas ratio): Kits 36946-01K, 36946-04K and 36941-01K.
  • Increased line pressure boost (diesel ratio): Kits 36946-02K and 36946-03K are recommended for all heavy-duty applications.
  • Kit 36941-01K works in early model "clicker" versions with screw-on boost valve end plate.
  • Kits 36946-01K, 36946-02K and 36941-01K include O-rings to provide additional protection against both cross leakage and oil exhausting through the valve body bore.
  • Valve
  • Sleeve
  • C6 Boost Valve  Kit 36946-03K
  • C6 Boost Valve  Kit 36946-03K

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.

C6 Boost Valve  Kit Vacuum Test Locations