Tightened all four upper control arm bolts on the Silverado yesterday, guess I'll do my next alignment or have my other buddy do it next time. Had a mystery thunk only in reverse and not repeatable after all this work I done and a slight pull to the right. Well, that's just where one camber/caster bolt was left just loose enough to be able to flap back and forth between it's maxes. Surprisingly drove awesome. Knocked one way out tightening them, got it back close but still need another alignment.