Suburban 3/4 Ton 4WD V8-305 5.0L (1986)
Brake Proportioning/Combination Valve: Technical Service Bulletins
Brakes - Height Sensing Proportioning Valve Adjustment
GMC NUMBER:
89-5-137
GROUP:
5 Brakes
DATE:
December, 1990
CORPORATE
NUMBER:
565001R
SUBJECT:
HEIGHT SENSING BRAKE PROPORTIONING VALVE ADJUSTMENT PROCEDURE
MODELS:
1984-85 C2 AND K2 SUBURBANS AND 1986-89 R2 AND V2 SUBURBANS
THIS BULLETIN CANCELS AND REPLACES GMC TRUCK SERVICE BULLETIN 86-B-93 DATED JUNE, 1986 (CORPORATE NUMBER
565001) TO ADD 1986-89 R2 AND V2 SUBURBANS AND TO UPDATE THE SERVICE INFORMATION. ALL COPIES OF 86-B-93 SHOULD
BE DISCARDED.
The brake balance on 1984-1985 C2 and K2 Suburbans can be adjusted in order to enhance rear braking performance under lightly loaded vehicle
conditions. 1986-89 R2 and V2 Suburbans were built with this new brake adjustment.
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. The following service procedure should also be used on all 1984-89 suburbans if the height
sensing linkage has been disconnected from the valve during routine service.
Important
For vehicles exhibiting a hard brake pedal feel with a cold engine or upon quick brake reapply, reference GMC Truck Service Bulletin 88-T-121 Dated
June, 1988 (Corporate Number 865005).
Figure 1
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 (See Figure 1).
