Brake Proportioning/Combination Valve: Adjustments

Fig. 9 Height Sensing Proportioning Valve:

Fig. 10 Adjustment Gauge Installation:

The height sensing proportioning valve must be adjusted whenever the valve and/or linkage is disassembled or removed for service. In addition, adjustment should be checked if excessive rear wheel lock-up is experienced with a lower than desired brake application rate when vehicle is at or near maximum GVWR.
1. Raise and support vehicle leaving wheels on, and allow axle to hang free (no load condition).
2. Remove lever retaining nut and disconnect lever from valve shaft, Fig. 1.
3. Rotate valve shaft to permit installation of correct adjustment gauge, Fig. 2, ensuring that ``D'' shaped hole of gauge is properly seated on valve shaft and that gauge tang engages mounting hole in valve. Adjustment gauges vary depending upon vehicle application. Correct gauge must be used to ensure proper operation of braking system.
4. Install lever on valve shaft by pressing plastic bushing and clip assembly over shaft serrations using C-clamp or suitable pliers. Do not press lever onto shaft using retaining nut, as adjustment of valve will be disturbed.
5. Install lever retaining nut and torque to 70---98 inch lbs.
6. Cut tang off adjustment gauge and allow valve to rotate freely.
7. Lower vehicle and test brakes.