Most alignment shops start out by turning the steering wheel to achieve the
correct toe in/out. Then, they adjust the tie rod ends on the other side of
the of the vehicle to correct the toe in/out. This results in moving the
center of the steering box. They then remove the steering wheel and point
it straight ahead. This works, sort of, on rear wheel drive vehicles, but
not on a GMC with front wheel drive. Makes them wander. To really do it
right, an adjustable drag link is very helpful. More complex than space
here permits for explanation in detail. Go on Jerry Work's web site, "The
dovetail joint", he has a very detailed alignment procedure there.
Jim Hupy
Salem, Oregon