Height-Sensing Proportioning Valve
Valve senses vehicle load conditions through relative movement between rear axle and body. See Figure and Figure. As vehicle load increases (resulting in decreased vehicle height), valve allows higher pressure to rear brakes, resulting in optimum front-to-rear brake pressure balance.
WARNING:
On vehicles with height sensing proportioning valve, use of aftermarket load leveling kits, air shocks, or modifications that change axle-to-frame distance will provide a false reading to valve. False readings may result in unsatisfactory brake performance.