| Subject: | Vehicle Lean Diagnostic Information |
| Models: | 1999-2006 Cadillac Escalade Models |
| 1999-2006 Chevrolet Avalanche, Suburban, Tahoe |
| 1999-2007 Chevrolet Silverado Classic |
| 1999-2007 GMC Sierra Classic |
| 1999-2006 GMC Yukon, Yukon XL, Yukon Denali, Yukon Denali XL |
This PI has been revised to add model years. Please discard PIT3098.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
This procedure should be followed to diagnose and correct customer complaints of vehicle leaning left or right. The same steps are followed whether the lean appears in the front, rear, or both ends of the vehicle. Generally, a vehicle's attitude can
be adjusted with the torsion bar adjuster bolts. In certain cases, however, other changes may be needed.
Recommendation/Instructions:
Measure fender wheel-opening heights, front and rear, to quantify vehicle lean.
Fender wheel-opening heights are related to, but distinct from, trim height (a.k.a. Z and D height). The front wheel-opening height is known as P height, and the rear wheel-opening height is know as R height. The P and R heights are not set at the factory,
nor is a specification given for them. However, they are the most direct and repeatable measurement of what a customer would see as the vehicle leaning.
Perform the following before measuring the fender wheel-opening heights:
| • | Make sure the vehicle is on a level surface, such as an alignment rack |
| • | Remove the alignment rack floating pins |
| • | Set the tire pressures to the pressure shown on the certification label. Refer to Label - Vehicle Certification in General Information. |
| • | Check the fuel level. Add additional weight if necessary to simulate a full tank. |
| • | To ensure proper weight distribution make sure the rear storage compartment is empty |
| • | Close the doors and hood |
P Height and R Height Measurements:
P height and R height are measured the same way. They are the distance from the ground to the highest point on their respective wheel-opening, going through the center of their respective wheel.
If the difference left to right, P and or R height is 12 mm or less no repairs are suggested as the vehicle is within specification. If the difference left to right exceeds 12 mm follow 1 of the 3 diagnostics below.
- If P height is more than 12 mm different left to right, and R height is more than 12 mm different from left to right.
| • | Check Z height and D height. See Trim Height Inspection Procedure. |
| • | If Z height is out of spec and D height delta is greater than 12 mm, adjust Z height until it is within spec and P and R height deltas are less than 12 mm. |
| • | If Z height is within spec but D height delta is greater than 12 mm, adjust Z height to reduce P and R height deltas to less than 12mm, staying within the Z height tolerances. If this is not possible, check front eye of rear leaf spring for matching
color-coded tape or paint. Both sides should be the same color. If not, switch springs side to side. If so, replace leaf spring on lower side only. |
| • | Recheck Z, D, P, and R heights. |
| • | If Z height is out of spec but D height delta is less than 12 mm, adjust Z height until it is within spec and P and R height deltas are less than 12 mm. If this is not possible, shim the front fenders and box as needed. |
| • | If Z height is within spec and D height delta is less than 12 mm, adjust Z height, within tolerance, until P and R height deltas are less than 12 mm. If this is not possible, shim body and/or pick-up box until P and R height deltas less than 12
mm. |
- If P height is within 12 mm left to right, and R height is more than 12 mm different from left to right
| • | Check Z height and D height. See Trim Height Inspection Procedure. |
| • | If Z height is out of spec and D height delta is greater than 12 mm, adjust Z height until it is within spec and P and R height deltas are less than 12 mm. |
| • | If Z height is within spec but D height delta is greater than 12 mm, adjust Z height to reduce P and R height deltas to less than 12 mm, staying within the Z height tolerances. If this is not possible, check front eye of rear leaf spring for matching
color-coded tape or paint. Both sides should be the same color. If not, switch springs side to side. If so, replace leaf spring on lower side only. |
| • | Recheck Z, D, P, and R heights. |
| • | If Z height is within spec and D height delta is less than 12 mm, shim body and/or pick-up box until P and R heights are within 12 mm left to right. |
- If P height is more than 12 mm different from left to right, and R height is within 12 mm left to right.
| • | Check Z height and D height. See Trim Height Inspection Procedure. |
| • | If Z height is out of spec and D height delta is greater than 12 mm, adjust Z height to spec. Recheck P, R, and D heights. |
| • | If Z height is within spec and D height delta is less than 12 mm, adjust Z height, staying within tolerance, until P height delta is less than 12 mm and R height delta is less than 12 mm. If this is not possible, add fender shims as necessary to
make P and R height deltas less than 12 mm. |
| • | If Z height is out of spec and D height delta is less than 12 mm, adjust Z height until within spec and P and R height deltas are less than 12 mm. If this isn't possible, check D height with Z height in spec. If D height delta is greater than 12
mm, then check front eye of rear leaf spring for matching color-coded tape or paint. Both sides should be the same color. If not, switch springs side to side. If so, replace leaf spring on lower side only. |
| • | Recheck Z, D, P, and R heights. |
| • | If Z height is within spec and D height delta is greater than 12 mm, shim front fenders to get P height delta less than 12 mm. |
| • | After all adjustments are done, perform a front-end alignment and check headlight aim. |
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
