The proportioning valve is actually a three part unit, containing a metering valve, pressure differential valve and brake pressure warning switch. If any of these functions fails, the unit must be replaced. It is not repairable. Two different types of valves were used. On models in the early 1970s, a D-type valve was used, in the late 1970's, a Type W was also used. They are similar in appearance and the only significant difference is in the method of holding open the valve during bleeding. Type W uses tool J-26869; type D uses tool J-23709. The valves are not interchangeable, however. In late 1983, the W-type became the only type used.
The valve is located on the frame rail, directly under the driver's position.
REMOVAL & INSTALLATION
See Figures 1, 2, 3, 4 and 5
- Disconnect the brake lines at the valve and plug them.
- Unbolt and remove the valve.
- Installation is the reverse of removal. Bleed the system.