D Height Measurement

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

1. With the vehicle on a flat surface, lift upward on the rear bumper 38 mm (1.5 in).
2. Gently remove your hands. Allow the vehicle to settle into position.
3. Repeat the jouncing operation 2 more times for a total of 3 times.
4. Measure the D height by measuring the distance between the rear axle and the jounce bumper (without Auxiliary Springs only). See Fig 1 .
5. Measure the D height by measuring the distance between the rear axle and the frame (with auxiliary springs only). See Fig 2 .
6. Push the rear bumper downward to 38 mm (1.5 in).
7. Gently remove your hands. Allow the vehicle to settle into position.
8. Repeat the jouncing operation 2 more times for a total of 3 times.
9. Measure the D height dimension.
10. The true D height dimension number is the average of the high and the low measurements. Refer to TRIM HEIGHT SPECIFICATIONS (REAR)  and TRIM HEIGHT SPECIFICATIONS (FRONT)  .
11. If these measurements are out of specifications, inspect for the following conditions:
    • Sagging front suspension. Refer to COIL SPRINGS.
    • Sagging rear leaf springs. Refer to LEAF SPRING REPLACEMENT (PASSENGER/CARGO) and LEAF SPRING REPLACEMENT (CUTAWAY/UPFITTER) .
    • Worn rear suspension components, such as leaf spring bushings. Refer to SPRING BUSHING REPLACEMENT .
    • Improper tire inflation.
    • Improper weight distribution.
    • Collision damage.

Fig 1: Measuring D Height (Without Auxiliary Springs)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Measuring D Height (With Auxiliary Springs)

Courtesy of GENERAL MOTORS CORP.