PIT3098E

Bulletin No.: PIT3098E
Date: Dec-2014
Subject:
Diagnostic Tips: Vehicle Body Tilt Or Lean
Models:
1999 - 2006 Cadillac Escalade Models
1999 - 2006 Chevrolet Avalanche, Suburban, Tahoe
2007 - 2013 Chevrolet Suburban HD
1999 - 2007 Chevrolet Silverado Classic
2007 - 2015 Chevrolet Silverado HD
1999 - 2007 GMC Sierra Classic
2007 - 2015 GMC Sierra HD
1999 - 2006 GMC Yukon, Yukon XL, Yukon Denali, Yukon Denali XL
2007 - 2013 GMC Yukon XL HD
With Torsion Bar Front Suspension
This PI was superseded to update Model Years. Please discard PIT3098D.
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 the vehicle's stance 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 known 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 perceive as a
leaning condition.
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.
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If the difference left to right, P and or R height is 1/2 inch (12 mm) or less no repairs are suggested as the vehicle is within specification. If the difference left to
right exceeds 1/2 inch (12 mm) follow 1 of the 3 diagnostics below.
1.
If the difference left to right, P and or R height is 1/2 inch (12 mm) or less no repairs are suggested as the vehicle is within specification. If the difference
left to right exceeds 1/2 inch (12 mm) follow 1 of the 3 diagnostics below.
1.1. Check Z height and D height. See Trim Height Inspection Procedure.
1.2. If Z height is out of spec and D height delta is greater than 1/2 (12 mm), adjust Z height until it is within spec and P and R height deltas are less than
1/2 inch (12 mm).
1.3. If Z height is within spec but D height delta is greater than 1/2 inch (12 mm), adjust Z height to reduce P and R height deltas to less than 1/2 inch
(12mm), staying within the Z height tolerance. 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.
1.4. Recheck Z, D, P, and R heights
1.5. If Z height is out of spec but D height delta is less than 1/2 inch (12 mm), adjust Z height until it is within spec and P and R height deltas are less
than 1/2 inch (12 mm). If this is not possible, shim the front fenders and box as needed.
1.6. If Z height is within spec and D height delta is less than 1/2 inch (12 mm), adjust Z height, within tolerance, until P and R height deltas are less than
1/2 inch (12 mm). If this is not possible, shim body and/or pick-up box until P and R height deltas less than 1/2 inch (12 mm).
2.
If P height is within 1/2 inch (12 mm) left to right, and R height is more than 1/2 inch (12 mm) different from left to right.
2.1. Check Z height and D height. See Trim Height Inspection Procedure.
2.2. If Z height is out of spec and D height delta is greater than 1/2 inch (12 mm), adjust Z height until it is within spec and P and R height deltas are less
than 1/2 inch (12 mm).
2.3. If Z height is within spec but D height delta is greater than 1/2 inch (12 mm), adjust Z height to reduce P and R height deltas to less than 1/2 inch
(12 mm), staying within the Z height tolerance. 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.
2.4. Recheck Z, D, P, and R heights.
2.5. If Z height is within spec and D height delta is less than 1/2 inch (12 mm), shim body and/or pick-up box until P and R heights are within 1/2 inch (12
mm) left to right.
3.
If P height is more than 1/2 inch (12 mm) different from left to right, and R height is within 1/2 inch (12 mm) left to right.
3.1. Check Z height and D height. See Trim Height Inspection Procedure.
3.2. If Z height is out of spec and D height delta is greater than 1/2 inch (12 mm), adjust Z height to spec. Recheck P, R, and D heights.
3.3. If Z height is within spec and D height delta is less than 1/2 inch (12 mm), adjust Z height, staying within tolerance, until P height delta is less than
1/2 inch (12 mm) and R height delta is less than 1/2 inch (12 mm). If this is not possible, add fender shims as necessary to make P and R height deltas
less than 1/2 inch (12 mm).
3.4. If Z height is out of spec and D height delta is less than 1/2 inch (12 mm), adjust Z height until within spec and P and R height deltas are less than
1/2 inch (12 mm). If this isn't possible, check D height with Z height in spec. If D height delta is greater than 1/2 inch (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.
3.5. Recheck Z, D, P, and R heights.
3.6. If Z height is within spec and D height delta is greater than 1/2 inch (12 mm), shim front fenders to get P height delta less than 1/2 inch (12 mm).
4.
After all adjustments are done, perform a front-end alignment and check headlight aim.
Warranty Information
The correction for this concern may be one of several repairs described in the diagnostic tips above. For vehicles repaired under warranty, please use the
appropriate warranty labor operation based on the actual cause and repair.
:
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.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may
occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools,
safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that
your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
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