aucivileng

My 03 Sierra has had a bad popping noise in it for several thousand miles now. It is very loud and I can feel it in the floorboard under my feet. I have taken it to a couple of mechanics and no one can solve the problem. I took it to a tire shop and they discovered that the bolts that connect the control arms to the frame were loose. They tightened them up but it didn't take long before it was back at it again. I did it myself the next time and it held for a little while but has since returned. I am thinking about replacing the control arm bushings as something is not allowing the bolts to stay tight. Has anyone else replaced these or had the exact same problem? I was also having the bumping sound in the I-shaft so I replaced it but the replacement seems to have a little slack in it? Has anyone else had this problem with an aftermarket I-shaft of have I done something wrong? Thanks!