Questions and Answers

GMC Sierra 1500 Pop Outs Q. Dear Sir, My truck is a 1997 GMC Sierra 1500 Series long bed extended cab, 4.3 with 19,000 miles. Recently I took it in for an alignment. The tech told me that the caster and camber were off . To correct the situation a pop out had to be done. I was charged for two pop outs.

My question is "What is this popout procedure"? All I can see is that the tie rod ends were adjusted. Other than that what can an owner look for? Should there be any visible signs one could look for?

B.H. Parker

A. There are "knock-outs" in the upper control arm bolt mounting brackets at the frame. The factory "net" builds these trucks on a jig so that all trucks leaving the plant are supposed to be the same. There are holes where the bolts go through at the upper control arms that can have a stamping knocked out to make it an elongated hole so the control arm is moveable out and in for caster/camber adjustment.

If you look at the bolts, you will see big washers that are drilled off center (cams). Rotating these will change the angles. Each bolt needs to have one knockout removed for a total of four.