Thermal Relief Device – Drivetrain

PROBLEM SOLVED! How to Protect a System From Both Pressure and Thermal Excursions

Schrader Pacific was contacted by a drivetrain manufacturer that needed to protect a hydraulic part-time four-wheel-drive axle against both overpressure and overtemperature.

Schrader Pacific developed an integrated valve with two relief modes, one utilizing a spring-loaded pressure relief valve (PRV) and one utilizing a resetting thermal relief device (TRD). In the event of either a high-pressure excursion (or____?), the PRV opens, holding the torque transmission to the design limiting(?). The TRD will trigger, reducing system power in the case of a thermal excursion; after the operating temperature returns to the normal operating range, the TRD reengages the drive.


  • Dual-purpose combination valve
  • Protection from over pressurization
  • Protection from thermal excursion

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