GM Service Manual Online
For 1990-2009 cars only

Z Height Measurement

  1. Lift the front bumper of the vehicle up about 38 mm (1.5 in).
  2. Remove your hands. Let the vehicle settle.
  3. Repeat this operation for a total of 3 times.

  4. Object Number: 156339  Size: SH
  5. For all vehicles, measure from the pivot bolt center line (2) down to the lower corner (5) of the steering knuckle (1) in order to obtain the Z height measurement (4).
  6. Push the front bumper of the vehicle down about 38 mm (1.5 in).
  7. Remove your hands.
  8. Allow the vehicle to rise.
  9. Repeat the operation for a total of 3 times.
  10. Measure the Z dimension.
  11. The true Z dimension number is the average of the high and the low measurements.
  12. • For RWD 15 series vehicles, the Z measurement is 92 mm (3.6 in).
    • For RWD 25 series vehicles, the Z measurement is 95 mm (3.7 in).
    • For 4WD 15 and 25 series vehicles, the Z measurement should be between 110-122 mm (4.4-4.8 in).

D Height Measurement

Important: The vehicle must be completely unloaded before the D Height is measured.


    Object Number: 156342  Size: SH
  1. Lift the rear bumper of the vehicle 38 mm (1.5 in).
  2. Remove your hands. Let the vehicle settle.
  3. Repeat this operation for a total of 3 times.
  4. Measure the D dimension (2). Measure from the bottom surface of jounce bracket (6) to the top of the axle jounce pad (3).
  5. Push the rear bumper of the vehicle downward 38 mm (1.5 in).
  6. Remove your hands. Let the vehicle rise.
  7. Repeat this operation for a total of 3 times.
  8. Measure the D dimension.
  9. The true D dimension is the average of the high and the low measurements.