Hoist Test

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/CV JOINT 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.)

1. Elevate the rear wheels slightly. Check to make sure both wheels will turn.

WARNING: THE ELECTRICAL POWER TO THE AIR SUSPENSION SYSTEM MUST BE SHUT OFF PRIOR TO HOISTING, JACKING OR TOWING AN AIR SUSPENSION VEHICLE. THIS CAN BE ACCOMPLISHED BY TURNING OFF THE AIR SUSPENSION SWITCH. FAILURE TO DO SO CAN RESULT IN UNEXPECTED INFLATION OR DEFLATION OF THE AIR SPRINGS WHICH CAN RESULT IN SHIFTING OF THE VEHICLE DURING THESE OPERATIONS.

CAUTION: The suspension must not be allowed to hang free. When the Constant Velocity (CV) joint is run at a very high angle, extra vibration as well as damage to seals and joints can occur;

2. Start the engine and place the range selector lever in DRIVE (D). Explore the speed range of interest using the drive/cruise/float tests; refer to Road Test. Road Test
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, a transaxle, wheel or tire concern is likely.