A tire pull can cause that problem. One way to find that is by switching the two front tires side-to-side. If it pulls the other way but there's no vibration, it can just be different rolling characteristics. You can usually get that problem to go away then by switching just the two left tires or two right tires. If there is a vibration or shimmy in the steering wheel, suspect a broken belt in one of the tires.
Worn lower control arm bushings can cause a pull by moving around and causing a change in alignment angles. That should have been found during the pre-alignment inspection or the post-alignment test drive. The problem certainly should have been noticed by the alignment mechanic.
The rack and pinion won't cause your problem unless it is loose on its mounts. A worn inner or outer tie rod end will let a wheel turn toward the center of the car on acceleration and away when braking. The entire rack assembly is not replaced to replace a worn inner tie rod end.
A real elusive cause of this problem that only affects GM cars is the removal of the cross member. Experienced mechanics will use spray paint to make "witness" marks so the cross member is bolted back up in exactly the same orientation. If that is not done, and it is moved to either side, that will move the lower control arms, ball joints, and bottoms of the struts sideways. That changes "camber" which is adjustable, or can be made adjustable if the struts are still original, but it also changes "steering axis inclination", (SAI). SAI is the inward tilt of the struts as viewed from the front of the car. There is no spec given on the alignment computer. All that is important is it must be the same on both sides. If it is not, even though camber can be corrected, it will leave the car very miserable to drive with its darting back and forth. That's why you need to look at the alignment printout.
Sunday, January 22nd, 2012 AT 8:33 PM