ACCELERATION NOISE/SHUDDER REPAIR PROCEDURES

MODEL AND YEAR: 1985-1986 V-6 CAVALIER, Z-24 AND CONVERTIBLE

Some 1985 and 1986 Cavaliers equipped with 2.8L V-6 engines may experience a vibration or shudder condition on hard acceleration as the vehicle reaches peak engine power and the suspension is at top of lift. The vibration or shudder goes away as vehicle suspension settles. This condition may be caused by increased drive axle angle during acceleration. To repair this condition, perform the "initial checks" then, if required, install new springs as outlined in this bulletin.

INITIAL CHECKS

Check tire pressure. Check for a mispositioned engine/transaxle assembly as follows. If measurements A & B, see Figure 1, are not within 6mm (1/4 inch) of each other on automatics or 3mm (1/8 inch) on manuals, the engine/transaxle assembly needs to be repositioned. To reposition, loosen all engine/transaxle mounts, jounce engine/transaxle assembly, and retorque as outlined in Figure 2.

Check that engine and transaxle mounts are tight.

Check for tight, left hand, inboard driveaxle joint as follows: Disconnect left inboard joint from transaxle. while holding the joint in the approximate same angle as when installed, compress and extend the joint through its travel limits. if binding is experienced, replace joint.

REPAIR PROCEDURES

1. Identify current springs on vehicle and record code and load rating for future reference.

2. Check trim height "Z" dimension, refer to Figure 3.

If "Z" dimension is between 25-35 mm, replace front springs with springs one load rating lower. See Table 1.

If "Z" dimension is greater than 35mm, replace front springs with springs two load ratings lower. See Table 1.

DROP ONE LOAD LEVEL DROP TWO LOAD LEVELS

"Z" = 25 - 35 MM 35+MM

3. Check trim height "K" dimension, refer to Figure 4.

- If "K" dimension is between 231-241 mm, replace rear springs with springs one load rating lower. See Table 1.

- If "K" dimension is greater than 241 mm, replace rear springs with springs two load ratings lower. See Table 1.

DROP ONE LOAD LEVEL DROP TWO LOAD LEVELS "K" = 231 - 241 MM 241 + MM

TABLE 1 - SELECTING SERVICE SPRINGS

FRONT SPRINGS REAR SPRINGS Rate - 27.0 Rate - 31/50 ----------- ------------ Load Load Part No. Code Rating Part No. Code Rating ------------------------------- --------------------------------- 14085586 FKH 4140 10026151 NSL 3000 14085585 FKF 3860 10021068 NPT 2785 14085584 FKD 3580 10021067 NPS 2570 14085583 FKC 3300 10021066 NPR 2355 14085582 FKB 3020 10021065 NPP 2140 14085581 FKA 2740

CHECKING BUMPER HEIGHT

Remove everything except jack and spare tire assembly from trunk. Make sure vehicle has a full tank of fuel or ad-4 compensating weight (one gallon of fuel weighs approximately 6 pounds). Set tire pressure to 28 PSI (if equipped with 13 inch wheels and tires, set tire pressure to 35 psi, refer to tire placard on the rear face of the driver's door). Jounce front and rear of vehicle. Check bumper heights as outlined in Figure 5.

HEADLIGHTS ALIGNMENT

Check headlight alignment and adjust if necessary.

CHECK FRONT SUSPENSION ALIGNMENT

Check front suspension alignment and adjust if necessary.

WARRANTY

For warranty purposes, use the following Labor Operations:

If front springs are replaced only, use labor operation T6178 at 2.3 hours, add .5 hours to adjust camber on one side, add 1.1 hours to adjust camber on both sides.

If front and rear springs are replaced, use labor operation T6179 at 3.0 hours, add .5 hours to adjust camber on one side, add 1.1 hours to adjust camber on both sides.

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.