I have a 1999 F250 Super Duty 7.3L 4X4 with 180k and service body on it. It is all stock with no mods. I just bought it for my business.

When I take off I hear a "clunk" or "thud" no matter how gentle or aggressive I accelerate. I had someone else get in and I watched when he took of from a stop and I saw the axle wrap up making that
"clunk". Has anyone out there experienced this?

Also I put new front brakes on it and it started pulling to the left when I applied them. So I figured the calipers needed replaced since they are original. Put new calipers on and same problem. Any suggestions?

And yes I have bled the holy @$%$ out of them. It however seem like there is still air in there but it never changes.