Suspension NVH Hoist Test Procedure

Suspension NVH Hoist Test Procedure

Warning:
^ If only one drive wheel is allowed to rotate, the speed must be limited to a maximum speedometer reading of 55 km/h (34 mph) since the actual wheel speed will be twice that indicated on the speedometer. Exceeding a speed of 55 km/h (34 mph) or allowing the drive wheel to hang unsupported can result in tire disintegration/differential failure, which can cause serious personal injury/extensive vehicle damage.

After a road test, it is sometimes useful to do a similar test on a hoist. (Use an axle hoist, not a frame hoist. An axle hoist will not change the driveline angles. If only a frame hoist is available, axle stands must be used.) Make sure the 4WD selector is in the 2WD mode on a 4WD vehicle.

Warning:
^ A vehicle equipped with a Traction-Lok differential will always have both wheels driving. If only one wheel is raised off the floor and the rear axle is driven by the engine, the wheel on the floor could drive the vehicle off the stand or jack. Be sure both rear wheels are off the floor. Failure to follow these instructions may result in personal injury.

1. Elevate the rear wheels slightly. Check to make sure both wheels will turn.
2. Start the engine and shift the transmission into DRIVE. Explore the speed range of interest using the drive/cruise/float tests. See road test in SUSPENSION NVH DIAGNOSIS. Suspension NVH Diagnosis
3. A coast down in NEUTRAL must also be conducted.
^ If the vehicle is free of vibration when operating at a steady indicated speed and behaves very differently in DRIVE and coast, an axle concern is likely.