I had a similar sound on a 78 fj40. Went through all previous suggestions plus. Someone on this forum ( I would like to give them credit but I forgot who it was) suggested the hood hinges. Never in a million years I thought that would be the problem. That stopped the thumping.
Just wanted to thank everyone who replied to my post!!!
Roadstr60 your suggestion was the one. I would of bet anything that was not the problem. Just like you said sounded just like a rubber mallet on the floor boards. Exhaust hitting the frame. What an easy fix, the bright side new spring...
After I check the hood hinges fingers crossed. Next all four wheels off the ground look for any rub marks again. My other option run it till it snaps, rips, cracks, twists, bends or just falls off...... then I'll know what the noise was.
In the beginning I did briefly check them not thinking that was it , I was more focused on the suspension. But now as I check things off the list I'll have to revisit them. Thanks
Manual locking hubs universals feel tight with pry bar driveshaft has no play you can't get them to clunk getting on and off the clutch. Two people bouncing on the bumper can't duplicate the noise????