Wheel Alignment Procedures
Measuring Wheel Alignment
Steering and vibration complaints are not always the result of improper alignment. One possible cause is wheel and tire imbalance. Another possibility is tire lead due to worn or improperly manufactured tires. Lead/pull is defined as follows: At a constant highway speed on a typical straight road, lead/pull is the amount of effort required at the steering wheel to maintain the vehicle's straight path. Lead is the vehicle deviation from a straight path on a level road without pressure on the steering wheel. Refer to Radial Tire Lead/Pull Correction in order to determine if the vehicle has a tire lead problem.
Before performing any adjustment affecting wheel alignment, perform the following inspections and adjustments in order to ensure correct alignment readings:
^ Inspect the tires for the proper inflation and irregular tire wear. Refer to Label - Vehicle Certification, Tire Place Card, Anti-Theft and Service Parts ID and Tire Diagnosis - Irregular or Premature Wear.
^ Inspect the runout of the wheels and the tires.
^ Inspect the wheel bearings for backlash and excessive play. Refer to Wheel Bearings Diagnosis.
^ Inspect the ball joints and tie rod ends for looseness or wear.
^ Inspect the control arms and stabilizer shaft for looseness or wear.
^ Inspect the steering gear for looseness at the frame.
^ Inspect the struts/shock absorbers for wear, leaks, and any noticeable noises. Refer to Struts or Shock Absorbers On-Vehicle Testing.
^ Inspect the vehicle trim height. Refer to Trim Height Inspection Procedure.
^ Inspect the steering wheel for excessive drag or poor return due to stiff or rusted linkage or suspension components.
^ Inspect the fuel level. The fuel tank should be full or the vehicle should have a compensating load added.
Give consideration to excess loads, such as tool boxes, sample cases, etc. If normally carried in the vehicle, these items should remain in the vehicle during alignment adjustments. Give consideration also to the condition of the equipment being used for the alignment. Follow the equipment manufacturer's instructions.
Satisfactory vehicle operation may occur over a wide range of alignment settings. However, if the setting exceeds the service allowable specifications, correct the alignment to the service preferred specifications.
Perform the following steps in order to measure the front and rear alignment angles:
1. Install the alignment equipment according to the manufacturer's instructions.
2. Jounce the front and the rear bumpers 3 times prior to checking the wheel alignment.
3. Measure the alignment angles and record the readings.
Important: When performing adjustments to vehicles requiring a 4-wheel alignment, set the rear wheel alignment angles first in order to obtain proper front alignment angles.
4. Adjust alignment angles to vehicle specification, if necessary.
Trim Height Adjustment
^ Tools Required
- J 42854 Trim Height Measurement Gage
Important: When adjusting either the right or left rear trim height the opposite side trim height will be effected.
Trim height should be measured with a full tank of gas and zero passengers or cargo.
An alignment hoist should be checked periodically to assure that both runners are the same height off the ground, side-to-side and front-to-rear.
1. Place the vehicle on an alignment rack.
2. Set the tire air pressure to the proper pressure.
3. Manually lift the rear of the vehicle up approximately 38 mm (11/2 inch), gently remove hands and let the vehicle settle.
4. Repeat the above step two more times for a total of three times.
5. Use J 42854 to measure the distance between the lowest point of the ball joint and the center of the front side of the lower control arm mounting bolt.
6. Manually push the rear of the vehicle down approximately 38 mm (11/2 inch), gently remove hands and let the vehicle settle.
7. Repeat the above step two more times for a total of three times. Measure both the right and left sides of the vehicle.
Front Caster and Camber Adjustment
^ Tools Required
- J 45938 Alignment Socket
1. The caster and camber adjustments are made by rotating the offset cam bolt and the cam in the slotted frame bracket in order to reposition the control arm.
Important: Before adjusting the caster and camber angles, jounce the front bumper three times to allow the vehicle to return to normal height.
Measure and adjust the caster and the camber with the vehicle at curb height. The front suspension Z dimension is indicated in Trim Heights.
For an accurate reading, do not push or pull on the tires during the alignment process.
2. Determine the caster angle (2). Be sure to compensate for frame angle where required.
3. Determine the positive camber (2) or negative camber (3) angle.
4. Adjust at the upper control arm.
5. Remove the pinned adjusting cam insert. Do not reinstall the cam insert.
6. Loosen the control arm cam adjustment bolts.
Notice: Refer to Fastener Notice in Service Precautions.
7. Using the J 45938 adjust the caster and the camber angle by turning the cam bolts until the specifications have been met. When the adjustments are complete, hold the cam bolt in order to ensure the cam bolt position does not change while tightening the nut.
^ Tighten the cam nuts to 155 Nm (114 ft. lbs.).
8. Verify that the caster and the camber are still within specifications. When the caster and camber are within specifications, adjust the toe.
Front Toe Adjustment