I recently bought a 96 F-250 2wd regular cab, LWB with 110,000 miles. It has a vibration when I brake normally anytime I'm going faster than 40 MPH. The whole truck shakes. The harder I brake, the more it shakes. If I brake lightly the vibration is less or non-existent. The vibration frequency seems to be higher (maybe double) the tire's rotation speed. It's hard to really tell where the vibration is coming from. There is also a slight vibration at highway speeds that I assume is a tire balance issue.

The brake pedal does not pulsate, the steering wheel doesn't vibrate and it's not that ABS feeling you get when the rear wheels lock up.

When I bought the truck I knew it needed radius arm bushings, which I replaced. I also replaced the front shocks, which were original. I repacked and preloaded the front wheel bearings as well. The vibration has not changed, however.

I checked the both front rotor's runout (less than 0.002") and thickness variation (less than 0.001"). I have 3" rear drums, which I haven't looked at yet. I have tried the unsafe maneuver of stopping the truck with the rear (emergency) brakes from 60 MPH and it was as smooth as silk.

I also visually inspected all the usual front-end suspects (tie rod, drag link, ball joints) and everything seems tight. There is considerable play in the steering wheel, though. I don't know if the steering box may be worn out or need adjusting.

Before I go spend $800 on new tires (it needs front tires anyway) and an alignment, I wonder if anyone out there has had a similar problem. The guy at Sears told me that if my front rotors are glazed, this could cause the problem.

Thanks in advance!
Mike

 

Other than looking at your back brakes, you've mentioned everything I would have suggested you check. However, locking up the back brakes is different than applying them progressively, if you follow my meaning. Could be you have a drum out of round. I would definitely check the rear brakes before anything else. The only other thing I wonder about is the front end. You said the steering is loose. Maybe your tie rod ends or ball joints are shot.

 

Thanks for your reply Todd. When I used the emergency brake, I didn't lock the back brakes up - I slowed down 'normally'. I had an alignment done today after checking the front end out myself. Other than the toe being a degree or two off, everything was fine and tight.

I'm going to pull the drums tomorrow and get them turned. I'll probably replace the rear shocks while I'm under there.

 

A clutch will do the same thing as well if it is glazed and isn't surfaced before putting a new one on. So, that could be a possibility too. I'd look into that if turning the drums doesn't work either.

 

I'd honestly get new drums. They are cheap enough now and it'd just be easier.

 

Thanks everyone for your help. I bit the bullet and got 4 new tires. The vibration is all but gone now. I imagine one of the drums may be slightly out of round but it's hardly noticeable now. Taking the drums off the 8600 GVW F-250 is a pretty major project... not the same as an F-150.

Mike