Alignment: Testing and Inspection
Trim Height Inspection
Trim Height Measurements
Trim height is a predetermined measurement relating to vehicle ride height. Incorrect trim heights can cause bottoming out over bumps, damage to the suspension components and symptoms similar to wheel alignment problems. Check the trim heights when diagnosing suspension concerns and before checking the wheel alignment. Perform the following before measuring the trim heights.
1. Make sure that the vehicle is on a level surface, such as an alignment rack.
2. Remove the alignment rack floating pins.
3. Set the tire pressure to the pressures shown on the certification label. Refer to Vehicle Certification, Tire Placard, Anti-Theft, and Service Parts ID Label (Application and ID).
4. Check the fuel level. Add additional weight if necessary to simulate a full tank.
5. Make sure that the rear compartment is empty except for the spare tire.
6. Close the doors and he hood.
Z Height Measurement
The Z height dimension measurement determines the proper ride height for the front end of the vehicle. Vehicles equipped with torsion bars use an adjusting arm in order to adjust the Z height dimension. Vehicles without torsion bars have no adjustment and could require replacement of suspension components. Jounce the front and rear suspension to obtain at least 38 mm (1.5 in) deflection, then allow the vehicle to settle.
Important: The left and right Z height difference should be no more than 12 mm (0.47 in).
1. Set the top edge of the level on the reference surface (Point A) of the steering knuckle.
2. With the level on the steering knuckle (C), extend the level directly under the rear of the rear of the front attachment bolt of the lower control arm (A).
3. While keeping the level in contact with the knuckle reference surface, adjust the level up or down until the bubble indicates it is horizontally level.
4. Extend a tape measure straight down from the center of the attachment bolt. The point where the tape measure and the level intersect is your first measurement.
5. Keep the top edge of the level on the reference surface of the steering knuckle (C) and move the level directly under the front end of the rear attachment bolt of the lower control arm (B).
6. Extend a tape measure straight down from the center of the attachment bolt. The point where the tape measure and the level intersect is your second measurement.
7. Average the 2 readings (add them together, and then divide by 3) and this result is your final Z height number.
8. Repeat steps 1 through 7, a total of 3 times, writing down the results.
9. Average the results (add them together, and then divide by 3) and this result is your final Z height number.
10. Compare your Z height number with the Service Information Z height specification. Refer to Trim Height Specifications (Trim Height Specifications).
Z Height Adjustment
1. For vehicles equipped with a torsion bar suspension turn the torsion bar adjuster bolt (1) clockwise to raise the and counterclockwise to lower the height adjustment.
2. For vehicles without torsion bars, replace damaged or worn components as necessary.
D Height Measurement
Important: The left and right D height difference should be no more than 12 mm (0.47 in.)
1. Lift the rear bumper of the vehicle up about 38 mm (1.5 in).
2. Gently remove your hands and let the vehicle settle.
3. Repeat this operation 2 more times for a total of 3 times.
4. D Height shall be measured as the perpendicular distance from the inside lip of the jounce bumper cup flange to the jounce bumper contact pad, or top of the rear axle "tube" when a jounce bumper pad is not used.
5. Lift the rear bumper of the vehicle up about 38 mm (1.5 in).
6. Gently remove your hands and let the vehicle settle.
7. Repeat this operation 2 more times for a total of 3 times.
8. Re-measure the D height as in step 4.
9. The true D height is the average of the measurement from step 4 and step 8. Refer to Trim Height Specifications (Trim Height Specifications).
10. If these measurements are out of specifications, inspect for the following conditions:
* Worn or damaged suspension components
* Collision damage