Re: Vibrations - stumped
TIRE AND WHEEL VIBRATION
Tire and wheel imbalance, runout and tire road force variation can cause vehicles to exhibit steering wheel vibration and/or seat vibration.
Visual inspection of the vehicle is recommended prior to road testing or performing any other procedure. Raise and support the vehicle.
Inspect for the following:
Verify correct (OEM) wheel and tire, as well as presence of wheel weights.
Inspect tires and wheels for damage, mud packing and unusual wear; correct as necessary.
Check and adjust tire air pressure to the pressure listed on the label attached to the driver's door opening.
NOTE: If a Noise & Vibration Analyzer is available, use it to diagnosis the issue during the road test.
NOTE: If the vehicle has been sitting for an extended period of time it is recommended to drive to warm the tires. This process could eliminate flat spots that can cause vibration.
Road test vehicle on a smooth road at and near the designated speed where legal speed limits allow. Lightly place hands on steering wheel at the 10:00 and 2:00 positions and observe for:
Steering wheel oscillation: clockwise/counterclockwise
Steering wheel high frequency movement: rapid vibration up and down
Seat high frequency movement: rapid vibration up and down
To rule out vibrations due to brakes or powertrain:
Lightly apply brakes at the designated speed; if vibration occurs or is enhanced, vibration is likely due to a brake concern. Shift transmission into neutral while vibration is occurring; if vibration is eliminated, vibration is likely due to a powertrain concern
TIRE/WHEEL BALANCE AND ROAD FORCE VARIATION
Balance the tire and wheel assemblies as necessary, and if wheel balance equipment is capable, also test for tire and wheel runout and road force variation following the wheel balancer manufacturer's instructions and using the information listed in Tire And Wheel Balance. Repeat the road test above to verify the vibration is repaired.
Tires that are out-of-round, or wheels that are not balanced, will cause a low frequency vibration.
Brake rotors that are unbalanced will cause a harsh, low frequency vibration.
Driveline vibration can also result from loose or damaged engine mounts.
Propeller shaft vibration increases as the vehicle speed is increased.
A vibration that occurs within a specific speed range is not usually caused by a propeller shaft being unbalanced. Defective universal joints, or an incorrect propeller shaft angle, are usually the cause of such a vibration.
Removing and re-indexing the propeller shaft 90° rear axle 45° trans case or front axle relative to the yoke may eliminate some vibrations.
Vibration at the rear of the vehicle is usually caused by a:
Damaged drive shaft
Missing drive shaft balance weight(s)
Worn or out-of-balance wheels
Loose wheel lug nuts.
Damaged axle shaft bearing(s)
Loose pinion gear nut
Excessive pinion yoke run out
Bent axle shaft(s)