Suburban 3/4 Ton 4WD V8-305 5.0L (1986)
Vacuum Brake Booster: Technical Service Bulletins
Brakes - Replacement Booster Push Rod Height Gage
GMC NUMBER:
89-T-51
GROUP:
5 - Brakes
DATE:
April, 1989
CORPORATE
NUMBER:
965005
SUBJECT:
BRAKE BOOSTER PUSH ROD HEIGHT GAGE
MODELS:
1982-89 LIGHT DUTY TRUCKS
A new brake booster push rod height gage (J37839) has been approved by Delco Moraine. The new gage is an essential tool and replaces tool J22647,
which should be scrapped. The new gage will be shipped to dealers in the April-May 1989 time frame.
FIGURE 1
The reason for the new gage is twofold
1.
The new gage locates on the chamfered sides of the booster push rod rather then the top of the rod. This is a more accurate reference point because
the push rod sides initiate the contact with the master cylinder primary piston (See Figure 1).
2.
The maximum and minimum push rod length tolerance was revised to reduce push rod free travel.
IMPORTANT:
These design change were made for all 1989 Delco Moraine vacuum boosters. The new gage can be used on all pre-1989 models with
Delco Moraine vacuum boosters.
Gage Procedure
1.
With master cylinderr removed and the brake booster still attached to the vehicle, gage the booster with 85.0 kPa (25 In. Hg.) vacuum or
maximum engine vacuum.
IMPORTANT:
Booster can be gaged without being installed on the vehicle, if a suitable vacuum source is available.
2.
Position gage (J37839) over piston rod as shown in Figure 1.
3.
Check for both the maximum and minimum rod length.
4.
If the rod length does not fall between the maxand minimum dimensions, replace with adjustable push rod P/N 5469384.
Parts are currently available from GMSPO.