FRT. SUSP. BOTTOMING NOISE (INSTALL AIR CYLINDER)

SUBJECT: FRONT SUSPENSION BOTTOMING NOISE (INSTALL AIR CYLINDER)

MODELS: 1983-93 G2 AND G3 VANS WITH 4.3L, 5.OL, 5.7L, 7.4L AND 6.2L ENGINES

THIS BULLETIN CANCELS AND REPLACES GMC TRUCK SERVICE BULLETIN #9l-3C-130 AND IS BEING REVISED TO INCLUDE THE 1992 AND 1993 MODEL YEARS.

CONDITION/CAUSE

On some 1983-93 G2 and G3 model vans equipped with 6.2L diesel engines (RPO LL4 or LH6) and gas engines (RPO LB4, L03, L05, or Ll 9) a condition may exist where the rubber jounce bumper makes an impact sound when it contacts the stop surface of the crossmember. This condition will usually be experienced on a vehicle traveling over large road bumps with capacity loads and sometimes at low temperatures.

CORRECTION

To correct this condition, urethane air cylinders (P/N 367762 - two required) may be installed inside the front coil springs. These air cylinders will help to cushion the front suspension on rough terrain.

SERVICE PROCEDURE

1. Follow the coil spring removal procedure in Section 3C Front Suspension, in the Light Duty Service Manual.

2. Clean the lower spring seat area of all rust where the air cylinder will seat.

3. Install the air cylinder inside the coil spring so that the protector plate is toward the upper control arm. This will allow the schrader valve to protrude through the hole in the lower control arm (Figure 1).

4. Install the coil spring by following the procedure in Section 3C Front Suspension, in the Light Duty Service Manual.

5. For most driving conditions, the air pressure should be maintained between 310 kPa (45 psi) minimum and 345 kPa (50 psi) maximum.

6. Air pressure in these cylinders may be increased or decreased to adjust vehicle trim and minimize jounce bumper impact on road bumps.

Effective with the following VIN, production began installing air cylinders in all G2 and G3 models equipped with the 6.2L diesel engine: 2GTEG25H4K4512023

SERVICE PARTS INFORMATION

Part Quantity Number Description Required ------ ---------------------- -------- 367762 urethane air cylinders 2

Parts are currently available from GMSPO.

WARRANTY INFORMATION

Labor Operation: E3037

Labor Time: 1.4 hrs.

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.