• Delayed Reverse
  • Soft shifts
  • Low line pressure
  • No Reverse
  • Harsh shifts
  • High line pressure


A worn boost valve sleeve allowing torque signal and/or Reverse pressure to cross leak or exhaust can cause these complaints.


Sonnax drop-in boost valve kit restores hydraulic integrity to the circuits and properly controls line rise.


Boost Valve Kit
Part No. 72754-01K

Factory-style sleeve, no O-rings

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

In GM 4T80-E units, the boost valve assembly is activated by torque signal pressure from the pressure control solenoid and Reverse pressure to aid in adjusting line pressure at the pressure regulator valve. This boost valve is continuously oscillating in the sleeve, which leads to wear and hydraulic leakage. When wear occurs, critical oil pressure is allowed to cross leak between the circuits or leak to exhaust. These leaks can result in either no line rise or an unwanted increase in line pressure. Sonnax boost valve kit 72754-01K restores hydraulic integrity and properly controls line rise.

  • Sleeve is manufactured from highly wear resistant aluminum, and the valve from anodized aluminum
  • Tight tolerances on the sleeve and valve maintain an ideal fit that prevents leakage
  • Drop-in Zip Valve parts install quickly and easily
Learn More About Zip Valve™ Drop-In Repairs
  • Valve
  • Sleeve
  • 4T80-E Boost Valve Kit 72754-01K
  • 4T80-E Boost Valve Kit 72754-01K

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.

4T80-E Boost Valve Kit Vacuum Test Locations