Z Height Measurement

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

IMPORTANT: For vehicles equipped with torsion bars, the Z height must be adjusted before the alignment.

The Z height dimension measurement determines the proper ride height for the front end of the vehicle. Vehicles equipped with torsion bars use a adjusting arm in order to adjust the Z height dimension. Vehicles without torsion bars have no adjustment and could require replacement of suspension components.

IMPORTANT: All dimensions are measured vertical to ground. Cross vehicle Z heights should be within 12 mm (0.47 in) to be considered correct.

Jounce the front and rear suspension several times to obtain at least 38 mm (1.5 in) deflection, then allow the vehicle to settle.

Fig 1: Locating Point A

Courtesy of GENERAL MOTORS CORP.

Point A is the contact surface of the steering knuckle for the levels.

Fig 2: Locating Steering Knuckle Components

Courtesy of GENERAL MOTORS CORP.

Set the top edge of the level on the reference surface of the steering knuckle (C) and extend the level directly under the rear end of the front attachment bolt of the lower control arm (A).
While keeping the level in contact with the knuckle reference surface, adjust the level up/down until the bubble indicates it is horizontally level.
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.
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).
Extend a tape measure straight down from the center of he attachment bolt. The point where the tape measure and the level intersect is your second measurement.
Average the 2 readings (add them together, then divide by 2) and write down the result.
Repeat steps 1 through 7 a total of 3 times, writing down the results.
Average the results (add them together, then divide by 3) and this result is your final Z height number.
Compare your Z height number with the Service Information Z height specification. Refer to Trim Height Specifications .