57 shortbed 3100 "clunking noise" unresolved

[milkman]

Restored truck, Hershey "lst"..bought it, had several issues that I resolved. Truck is "ready to roll"..but: Down the street, in any gear, I get a "metal on metal" clunk. First I thought the jack handle, was down under the tank?..bap...bap.. Nope.. searched underneath carefully for loose bolts, etc. Seems to come when it "wants" to..even with apparently the slighest imperfection in the black top street..a metal on metal "clunk"... engine is fine only happens when it is driving. It's not a tiny tap tap thing..it's a very clearly heard, "bang" like you hit a fender with a spanner wrench or something like that. Comes from, as we can hear, or tell, behind the passenger's seat, towards the rear.
Any suggestions would be greatly appreciated. Thanks for your time. Want to get a little cruising time in, before the snow flys. John (milkman):confused:

[BamaNomad]

Have you checked the spring bushings? (front and rear)? What about the U-joints for wear/sloppiness?

[Dragsix]

X2. I was thinking shocks, shackles and busings, u- joint, ball joint with the sound traveling down the frame.

[WagonCrazy]

X3-shocks, shackles and bushings, u- joint
Check them all.
Put a go pro camera mounted on a magnet under there and run down some rough roads.

had a similar situation on my Nomad as it was just roadworthy, turned out to be side of coilover spring flexing and hitting the half shaft (c4 corvette rear end) whenever the shock got close to bottom travel. An adjustment was made at top mounting point of coilover and it's resolved now.

Check anything that moves back there closely. Its gonna be obvious when you find it. (with that loud of a clunking noise).