[my67c20]

Damn mysterious noises. Ran into a similar situation years ago that sometimes when I hit a bump i would get a loud thud. Parked the truck checked all the suspension parts, welds, etc. Found a few sketchy things repaired them, but the noise still existed. So I mentally tried to keep track of what road and what I was doing on the road that recreated the thud on a regular basis. Found the secret turn that I could duplicate the noise, but I still could not find the issue. Took everything out of the bed and the cab that could move, noise was still there. Well one day my wife was following me home and she tells me that when I made the turn it looked like the bed was going to fall off. Low and behold, the thud I kept hearing was the left front corner of the bed, slamming into the cab every time i turned left and hit any kind of bump. Long story short, check every nut and bolt.