Subject: | Steering Pull, Lead Left on Acceleration and Lead Right on Deceleration |
When servicing the vehicle with the VIN you entered, the following diagnosis
might be helpful if the vehicle exhibits the described symptoms.
Condition/Concern:
Vehicle may torque steer to the left with aggressive acceleration, and/or may
steer to the right with deceleration.
Recommendation/Instructions:
Items to check when performing initial vehicle inspection:
- Check tire pressures and verify conformance to 30 psi. Check for visible
tire damage.
- Verify there are no brake drags present by putting vehicle on frame lift
and rotating tires
- Examine front suspension for any visible indications of damage.
- Observe front suspension upper control arm alignment tabs and verify the
drilled hole in the alignment is centered over frame’s alignment pin. Verify
all control arm bolts are tight.
- Confirm that the rear suspension air leveling system is operating. With
the ignition on and the vehicle at curb weight, there should be pressure in the rear
shock absorber air bags. If an air line is removed at the rear shock and air escapes
until both bags go flat, the system is likely working. Reinstall air line, turn ignition
on, and weight for air compressor to energize air supply.
- Verify that the steering wheel is accurately centered when the vehicle
is going straight. This can be done on a known flat, no crown, road during a no load
condition at speeds between 25 and 40 mph. The preferred method would be to do this
on an alignment rack.
- Measure the front wheel opening heights to ground. With tires at 30 psi,
full load of fuel, and no occupants, measure from ground to highest point of the wheel
opening. With the vehicle in the described condition, it is typical that the vehicle
will have a lean with the right side being high. Right opening heights are typically
910 mm +/-5 mm (35.8 in +/- 0.2 in). Left opening heights are typically 900 mm +/-5
mm (32 in +/- 0.2 in). A 10 mm (0.39 in) difference, right side high is typical.
- Inspect idler arm and bracket. Verify that there is no excessive play.
- Examine the steering intermediate shaft and the joint between the upper
and lower intermediate shafts. There must be no play in this attachment.
After verifying all of the above, and that the vehicle still pulls left during
acceleration:
- Loosen all three steering attachment bolts, do not remove. Push upward
on the steering relay rod at the pitman arm joint and retorque the steering gear attachment
bolts at the same time.
- Put the vehicle on an alignment rack. Reset the front trim heights by
turning the two torsion bar adjuster bolts. With the tires at 30 psi, full fuel,
and no occupants, adjust so that both left and right front wheel openings have a relative
height to ground of 910 mm (35.8 in). In Z height terminology, this will put the
LF Z height at 116 mm (4.57 in) and the RF Z height at 111 mm (4.37 in). It is probable
that the vehicle will require a left side torsion bar adjuster change to 15592574
(White stripe).
- Set front alignment as follows:
Right front caster = +3.5 degrees
Left front caster = +2.8 degrees
Camber, both sides = +0.25 degrees
Total Toe = +0.1 degrees
Tolerance is +/- 0.1 degrees on all measurements. Caster is ground (not frame
compensated)
Please follow this diagnosis 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. If these steps do not resolve the condition, please contact
GM TAC for further diagnostic assistance. This diagnostic approach was developed for
the vehicle with the VIN you entered and should not be automatically be used for other
vehicles with similar symptoms.
Models:
(02, 03, 04 GMC Denali, Denali XL, Yukon, Yukon XL) and (02, 03, 04 Cadillac
Escalade, Escalade EXT)