I have a 1993 F-250 XLT, 4X4, 7.5L 460 tjat my father gave me and whenever I start to slow down going anything over 45 mph the whole truck starts to shake. I've asked what it could be because I thought it might be the rotors, but he said that he had replaced them before and the problem persisted. I'm trying to figure out what the problem might be so I can fix it. Any input would be appreciated. Thanks.

 

Are you certain they were replaced? Were they replaced with new rotors? Were all of them replaced? What about the pads? Are they still in good shape, or in need of replacement?

Do you only get the vibration while braking?

 

He replaced the ones in the front with new rotors and it continued. As far as the pads, I checked them when I got it and they were still in good shape. And yes it only happens when I'm braking from anything over 45. If I'm going 25-30 it's not bad.

 

Check the rear brakes as well. Also verify that all of your calipers are properly installed. Verify the rotors are properly installed as well. If they weren't seated fully, so that it isn't perpendicular to the ground, that may be causing a problem too.

 

Sometimes can be caused by loose steering components. Check tie rods, ball joints, etc...

 

When I going about 30 mph to 40mph the truck will start shaking the front end unless I stomp the grass and fly right thru up to about 50 mph and then it will not do it . I've tried steering damper or stabilizer and that does not seem to help my situation do I need to try something else or oh yes my truck does have a 6 in lift with 40 in. super swampers on it

 

Try applying the parking brake at about 45mph. If it vibrates, the problem is that the rear drums are out of round...