The Diesel Stop banner
1 - 6 of 6 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
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.
 

·
Super Moderator
Joined
·
26,504 Posts
Welcome to TheDieselStop

Your clunk on takeoff is likely the slip joint on the driveshaft (assuming you have a 2-piece driveshaft). A certain amount of axle wrap is normal, but you should check your rear suspension components and fasteners (u-bolts) to be sure they're tight. The usual fix if you don't find loose components is to lube the splines at the slip joint with teflon based grease. Ford sells a small tube as PN XG-3 (should be a lifetime supply). Don't go nuts with the grease, as that can cause the slide to seize up if there's too much between the end of the shaft splines and the bottom of the socket (similar to a hydrolock).

On the brake pull. There are slide pins on the calipers that can seize up causing drag. If you put new calipers on, that would eliminate (theoretically) the caliper pistons hanging up. Also, brake hoses can deteriorate and cause problems in not allowing the caliper to release (acting like check valves). I would pull the slide pins and be sure they're not hanging up and lightly lube them with silicone grease. No need to remove the calipers completely to do that, IIRC.

Good luck
 

·
Registered
Joined
·
2,195 Posts
I was gonna guess loose rear U-bolts.

This diagram shows the torque specs for 1/2-ton trucks, so yours should be slightly tighter:

 

·
Super Moderator
Joined
·
26,504 Posts
The correct torque spec for axle u-bolt nuts is 185 ft-lb on a SuperDuty. It's worth checking.
 
1 - 6 of 6 Posts
Top