Lift Test
After a road test, it is sometimes useful to do a similar test on a lift.
When carrying out the high-speed shake diagnosis or engine accessory vibration diagnosis on
a lift, observe the following precautions:
WARNING: If only one drive wheel is allowed to rotate, speed must be limited to
55 km/h (35 miles/h) indicated on the speedometer since actual wheel speed will be twice
that indicated on the speedometer. Speed exceeding 55 km/h (35 miles/h) or allowing the
drive wheel to hang unsupported could result in tire disintegration, differential failure,
constant velocity joint and driveshaft failure, which could cause serious personal injury
and extensive vehicle damage. Failure to follow these instructions may result in personal
injury.
CAUTION: The suspension should not be allowed to hang free. When the CV
joint is run at a very high angle, extra vibration as well as damage to the seals and joints
can occur.
The rear suspension lower arm should be supported as far outboard as possible. To bring the
vehicle to its correct ride height, the full weight of the vehicle should be supported in the rear
by floor jacks. <<100-02>>
1 . Raise and support the vehicle. <<100-02>>
2 . Explore the speed range of interest using the Road Test Quick Checks as previously
described.
3 . Carry out a coast down in neutral. If the vehicle is free of vibration when operating at a
steady indicated speed and behaves very differently in drive and coast, a transmission concern
is likely.
Note, however, that a test on the lift may produce different vibrations and noises than a road
test because of the effect of the lift. It is not unusual to find vibrations on the lift that were not
found in the road test. If the condition found on the road can be duplicated on the lift, carrying
out experiments on the lift may save a great deal of time.
Symptom Chart
High-speed shake
Possible Source(s):
•
Wheel end vibration.
•
Engine/transmission.