Owners of 2015-2018 GMC Canyon vehicles equipped with a 3.6L engine and 8L45 automatic transmission may comment about a vibration and/or noise heard during hard acceleration at speeds of 48-52 mph. The condition may be caused when the driveline angle gets extreme during axle wind-up, resulting in 2nd order vibration.
The fix involves installing a tapered shim between the axle and leaf springs to adjust the angle.
Before performing the service, check the following:
- Vehicle trim height compared to specification
- Check to see if aftermarket modifications have been performed that may affect driveline working angle.
- Inspect for accident damage that may affect the position of the axle, propeller shaft support bearing o transmission or transfer case.
1. Inspect the leaf springs, mount bushings and mounting hardware for excessive wear/damage.
2. Inspect the structure to which the suspension attaches to ensure that no deformities/damage exists.
3. Inspect the propeller shaft U-joints for damage.wear.
4. Inspect the transmission mount for damage/wear.
5. Raise the vehicle.
6. Using a hydraulic jack stand, support the rear axle.
7. Place a C-clamp on each end of the leaf spring and tighten so that tension is applied.
8. Remove the lower shock absorber nut.
9. Remove the rear spring anchor plate.
10. Lower the hydraulic jack stand just enough to be able to slide the 2-degree shim under the spring and the bolt up through the hole of the spring. Note: The thicker end of the shim must be placed toward the front of the truck to bring the pinion nose down.
11. Remove the center bolt from the leaf spring pack.
12. Install the tapered shim and the supplied bolt up through the hole of the spring. Tighten the bolt’s nut to 74 ft.-lbs., plus an additional 130 degrees.
13. Install the rear spring anchor plate.
If brake-induced shudder is found, it may be necessary to remove the 2-degree shim and install a 1-degree shim.
P/N ......................... PART
84375734................. shim kit (1 degree)
84131588................. shim kit (2 degree)
