2004 Chevy Suburban 5.3 flex. Heard a random knocking noise coming from what seems like the front drivers tire area. Its an older truck and need a new front end so I did all that. Brand new axle shafts, upper control arms, lower ball joints, wheel bearings, complete tie rods, and sway bar links, then got it aligned. Noise is still there. It doesn't happen on turns or bumps. The noise mainly happens randomly at any speed going straight on flat smooth roads. I can kind of feel the thumps on my left foot when it happens but not always. I also checked the body mount bushings and they all seem great. I have spent about 3 hours under there looking for any metal on metal contact points and have found nothing. The sound is always random and does seem to go with the rotation of the tires. The sound is always random and will sometimes knock several times in a row or once or twice then stop. Then comes back at random and repeats. The sound does not seem to be there when you first start driving it. Seems like it starts making noise around 10 miles after its driven. Applying the brakes makes no difference in the sound and the brakes do not seem to start the knocking. It is a loud noise and seems to be getting worse and more frequent. I'm stumped. Please help! ...just drove 50 miles to record sound and of course it didn't do it. Ugh.

 

I'd check front diff. mounts, trans mounts, etc. . Also inner fender panels, covers and skid plates if you have them. Pry things to look for looseness, especially heavy parts like front diff. mounting bushings.

 

Thank you! I checked all of those yesterday and nothing was loose. Noise came back again today on the highway for a few seconds and the noise was definitely hitting faster and indicating it is something dealing with the rotation of something. This is insane.

 

Did you manage to solve it? My 04 suburban does the same.

 

Nope. I hit a deer and totalled the truck. I'm 90% sure it was a bad piston ring.