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Home >> GMC >> 1978 >> Forward Control 4.8L Eng VIN T, Standard Trans >> Repair and Diagnosis >> Brakes >> Brakes Control Systems >> Hydraulic System Control Valves >> Operation >> Proportioning Valve

Proportioning Valve

Valve operates by restricting, at a given ratio, hydraulic pressure to rear brakes when system hydraulic pressure reaches a certain point. This improves front-to-rear brake balance at high speed braking, when a percentage of rear weight is transferred to front wheels. Valve reduces rear brake pressure, and delays rear wheel skid. On light brake application, valve allows full hydraulic pressure to rear brakes.