GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC Suburban - 2WD 🢒 Suspension 🢒 Tires and Wheels 🢒 Trim Height Inspection

Z Height

Trim height is a predetermined measurement relating to vehicle ride height. Incorrect trim heights may cause symptoms similar to alignment problems. Check the trim heights when you diagnose steering or vibration complaints.

The Z dimension measurement determines the proper ride height for the front end. The Z dimension is different for RWD vehicles and S4WD or F4WD vehicles. The S4WD and F4WD vehicles have different points of measurement to determine Z height. Use the torsion bar adjusting arm in order to adjust Z height. RWD vehicles have no adjustment and could require replacement of suspension components.


Object Number: 88 Size: SH

On RWD vehicles, measure Z height from the center line of the bolt of the front lower control arm down to the lower inboard corner of the ball joint. Trim all Z heights at 89.0-101 mm (3.5-4.0 in).


Object Number: 91 Size: SH

On S4WD and F4WD vehicles, measure Z height from the center line of the pivot bolt (1) down to the lowest inboard edge of the steering knuckle (2).


Object Number: 92 Size: SH

For S4WD and F4WD vehicles, use the following measurements:

    • K1 and K2 models (except K10906 with L65 or K20906 with C6P) trim the Z height at 151.0-163.0 mm (5.9-6.4 in).
    • K1 and K2 models (K10906 with L65 or K20906 with C6P) trim the Z height at 139.0-151.0 mm (5.5-5.9 in).
    • K3 models trim the Z height at 139.0-151.0 mm (5.5-5.9 in).

Z Height Measurement

Measure the Z height using the following procedure:


    Object Number: 130874 Size: SH
  1. Lift the front bumper of the vehicle up around 38 mm (1.5 in).
  2. Gently remove your hands. Let the vehicle settle by itself.
  3. Repeat the jounce operation two more times for a total of three times.
  4. Measure the Z dimension.
  5. Push the front bumper of the vehicle down about 38 mm (1.5 in).
  6. Gently remove your hands. Let the vehicle rise by itself.
  7. Repeat the jounce operation two more times for a total of three times.

    8. Important: True trim height is the average of the high and low measurements.

  8. Measure the Z dimension.
  9. Find the average of the high and low measurements. This is the true Z dimension.

D Height

The D dimension measurement determines the proper rear end ride height. There is no adjustment procedure. Repair may require replacement of suspension components.


Object Number: 93 Size: SH

D Height Measurement

Measure the D height using the following procedure:


    Object Number: 130875 Size: SH
  1. Lift the rear bumper of the vehicle up around 38 mm (1.5 in).
  2. Gently remove your hands. Let the vehicle settle by itself.
  3. Repeat the jounce operation two more times for a total of three times.
  4. Measure the D dimension.
  5. Push the front bumper of the vehicle down about 38 mm (1.5 in).
  6. Gently remove your hands. Let the vehicle rise by itself.
  7. Repeat the jounce operation two more times for a total of three times.

    8. Important: True trim height is the average of the high and low measurements.

  8. Measure the D dimension.
  9. Find the average of the high and low measurements. This is the true D dimension.