Usage:
768C, 772B, 776 Tractors;
769C, 773B, 777, 785 Trucks
Description of Change: The nylon adjusting ring used in the 9D8098 Air Control Valve Group (Secondary/Emergency) is being replaced by a brass adjusting ring (see Illustration 1). The nylon adjusting ring could become cross-threaded in some applications and the valve, part of the 6G9060 Brake Control Group, could lose correct adjustment. The brass adjusting ring will help prevent this loss of adjustment.
Illustration 1. 9D8098 Air Control Valve Group (Secondary/Emergency).
Adaptable To: The 4D5252 Adjusting Ring (Brass) is a direct replacement for the 5T1085 Adjusting Ring (Nylon) used in the 9D8098 Air Control Valve (Secondary/Emergency). If a new brass adjusting ring is installed, use the following procedure to adjust the valve correctly.
Procedure To Adjust The Secondary Brake Control Valve
1. The brake air system must be at specified operating pressure and the secondary (emergency) brake lever in the "OFF" position.
2. Measure the brake system pressure at the 9D8098 Air Control Valve inlet port.
3. Adjust the 4D5252 Adjusting Ring (Brass) until the air pressure at the outlet port of the valve is the same as or within minus 34 kPa (5 psi) of the system pressure.
Illustration 2. Adjust the 2B1016 Spring.
4. When the brake air system is at specified operating pressure and the secondary (emergency) brake control lever is in the full "ON" position, the air pressure at the outlet of the valve should be 17 ± 17 kPa (2.5 ± 2.5 psi).
5. When the 9D8098 Air Control Valve (Secondary/Emergency) is adjusted and installed, adjust the 2B1016 Spring (see Illustration 2) so that the brake lever returns to and remains in the "OFF" position.