sonnax-black Facebook-color LinkedIn-color maillink printlink r_and_r_only SERVOFIX-logo-web Twitter-color VBFIX-logo-web video-logo-web warranty_only Youtube-color


  • C1 Clutch hub wear
  • Lack of C1 clutch control
  • Harsh Forward
  • Delayed bump on Forward


The OE valve has a fixed flow rate, while C1 clutch pressure leaks to exhaust.


The Sonnax kit includes a PTFE seal to prevent C1 oil loss to exhaust. The new valve changes the fixed flow rate to a regulated flow rate.


C-1 Valve & Seal Kit
Part No. 37000-05K

Feb 2004 & earlier pumps

View Instructions

The OE C1 clutch control valve has a fixed flow rate and no seal at the large spool to prevent hot fluid loss. The Sonnax updated valve 37000-05K controls the fill and exhaust rate of the C1 clutch as well as reducing loss at the valve bore. The regulation contour of the Sonnax valve provides a controlled fill to reduce harsh engagements common to cold weather, long sit or reverse to forward abuse conditions. Controlling the flow rate reduces wear on the C1 clutch hub. Once the valve is open, the C1 flow is increased over OE to overcome fluid loss at the drum. The valve also has a PTFE seal to prevent incoming pressure loss to exhaust at the pump casting, which can occur under hot abuse conditions.

  • Valve changes the fixed flow rate to a regulated flow rate, reducing wear of the C1 clutch hub.
  • PTFE seal prevents C1 oil from leaking to exhaust.
  • This is a drop in replacement, with no bore modifications required.

Fits pump stators manufactured up to February 2004. Does not fit No. 29541135 or later pump stators.

  • C1 Clutch Control Valve
  • PTFE Seal
  • 37000 05k combo
  • 37000 05k