ASE A4 Suspension and SteeringWheel Alignment Diagnosis, Adjustment, and RepairHard
A technician is performing a four-wheel alignment on a vehicle with a solid rear axle. The alignment machine indicates a rear thrust angle of +0.4 degrees, with a specification of 0.0 degrees +/- 0.1 degrees. Which of the following is the most appropriate action for the technician?
- AAdjust the rear camber to bring the thrust angle into specification.
- BAdjust the individual rear toe settings to correct the thrust angle.
- CInspect for bent axle housing or shifted suspension components.
- DAdjust the front caster to compensate for the rear thrust angle.
Show answer & explanationAnswer & explanation
Correct answer: C. Inspect for bent axle housing or shifted suspension components.
On a vehicle with a solid rear axle, the thrust angle is typically non-adjustable. A significant thrust angle indicates a problem with the axle's mounting, the axle housing itself being bent, or other structural damage. Unlike independent suspensions, individual rear toe adjustments are not possible to correct thrust angle on a solid axle.
Why the other options are wrong
- A. Rear camber is often non-adjustable on solid axles, and even if it were, it would not directly correct thrust angle.
- B. Individual rear toe adjustments are not possible or effective on a solid rear axle to correct thrust angle, as the wheels are fixed relative to each other on the axle.
- D. Front caster adjustment does not correct a rear thrust angle issue.
Solid Rear Axle Thrust Angle
On vehicles with a solid rear axle, the thrust angle is typically non-adjustable. If it's out of specification, it indicates structural damage or shifted components.
- Solid axle thrust angle is fixed.
- Out-of-spec indicates bent axle, shifted mounts, or frame damage.
- Requires repair or replacement of components, not adjustment.
Memory trick: Solid axle's thrust, if it's off, means components are structurally rough.