BRAKE HEIGHT SENSING VALVE ADJUSTMENT PROCEDURE

VEHICLES AFFECTED: 1984-85 C/K 20/25 Suburbans ---------------------------

The brake balance on 1984-85 C, K-2 Suburbans can be adjusted in order to enhance rear braking performance under lightly loaded vehicle conditions.

In order to change brake balance, it will be necessary to adjust the height sensing brake proportioning valve. In addition, burnishing the brakes following the procedure below may be beneficial on some vehicles.

SERVICE PROCEDURE

Note: Always make sure that the brakes are operational after performing brake work and before returning the vehicle to service.

- Raise vehicle, axle must be allowed to hang free (no load condition).

- Remove nut and disengage lever assembly from valve shaft (Figure No. 1).

- Rotate valve shaft to permit installation of plastic adjustment gauge. Centre 'D' shaped hole of gauge must seat over 'D' shape of the valve shaft and gauge tang must be positioned in valve mounting hole (Figure No. 2).

- Reinstall lever assembly to the valve shaft utilizing a 'C' clamp or channel lock pliers to seat lever nylon bushing to serration on the valve shaft.

Note: DO NOT DRIVE THE LEVER ONTO THE SHAFT USING THE ATTACHING NUT. DOING SO MAY RESULT IN IMPROPER VALVE SETTING.

- Reinstall valve shaft nut and torque to 8 - 11 N.m (70 - 98 in. lbs.)

- Cut gauge tang from body of the adjustment gauge to allow the valve assembly to rotate freely (Figure No. 3).

- Lower vehicle and test brakes.

PARTS INFORMATION

Model P/N Description Code Colour ----- --- ----------- ---- ------ C20906 14061394 Gauge A Green K20906 15548904 Gauge E Yellow

BRAKE BURNISHING

- On dry clean level roadway, accelerate to 90 km/h (55 mph), observe traffic following and when its clear

- Apply brake at a deceleration rate of 2.45 m/sec (8 ft/sec/sec) until vehicle speed is 40 km/h (25 mph). A decelerometer must be used to achieve the proper deceleration rate.

- Repeat this procedure at 1.6 km (1 mile) intervals 15 times.

Declerometers are available from various sources, one of which is:

General Motors Dealer Equipment Program 1-800-263-3999

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.