Suspension (Front) - Bottoming Noise

91chevy25

Number: 91-379-3C

Section: 3C

Date: AUGUST 1991

Corporate Bulletin No.: 163301


Subject: FRONT SUSPENSION BOTTOMING NOISE


Model and Year: 1983-89 G2,G3 TRUCKS WITH 6.2L DIESEL ENGINE 1983-91 G2, G3 TRUCKS WITH 4.3L, 5.OL, 5.7L AND 7.4L ENGINES


THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 86-106, DATED JULY 1986. THE USE OF THE AIR CYLINDER WITH GAS ENGINES HAS BEEN ADDED AS WELL AS A LABOR OPERATION. ALL COPIES OF 86-106 SHOULD BE DISCARDED.

On some G2 and G3 model vans equipped with 6.2L diesel engines (RPO LL4 or LH6) and gas engines (RPO LB4, L03, L05, or L19) a condition may exist where the rubber jounce bumper becomes very hard in low ambient weather and 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.

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.

Figure 1:

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 VINs, production began installing air cylinders in all G2 and G3 models equipped with the 6.2L diesel engine.

2GBEG25C6K4130794

SERVICE PARTS INFORMATION:

Part Number Description Quantity Required

367762 urethane air cylinders 2

Parts are currently available from GMSPO.

WARRANTY INFORMATION:

Labor Operation: E3037

Use applicable labor times guide for labor hours.