Brake Proportioning/Combination Valve: Description and Operation

Fig 35 Type 3 Proportioning Valve Identification:

Proportioning Valve With ABS And Non-ABS TLEV:

There are two proportioning valve assemblies used in each vehicle. Due to differences in thread sizes, each proportioning valve has a different part number. During any service procedures identify valve assemblies by supplier part number and or the color identification band.

Proportioning valves balance front to rear braking by controlling at a given ratio, the increase in rear brake system hydraulic pressure above a preset level (split point). Under light pedal application, the proportioning valve allows full hydraulic pressure to be applied to the rear brakes.

Antilock Proportioning Valve (Left Side Shown):

On vehicles equipped with antilock brakes, the proportioning valves are located at the rear of the vehicle. The proportioning valves are mounted directly in-line with the chassis brake tube going to each rear brake of the vehicle.

Fig 4 Type 3 Master Cylinder. Less ABS:

The non-antilock master cylinder is a four outlet design with two screw-in proportioning valves attached directly to the inboard side of the master cylinder housing.

The master cylinder on vehicles equipped with antilock brakes is a two outlet design. This antilock brakes master cylinder does not have the proportioning valves mounted on it.