allinon72

Just bought a 05 FX4 and right around 60mph, I get a vibration from the rear that dances the bed all around. Any idea what this might be?

papa tiger

Ck tires and ujoints first. Tire flat spot, sidewall bulge, loose joints good as any place to start, even rotate and rebalance them. Especially if they is larger sizes, can't hardly get perfect on some sets. Look at the sizes of the weights ;inside and outside front and back. If a tire has really big ones on it and the rest seem perty normal it's probably your culprit. Had belts squirm once or twice. Nasty little things. Nasty little flats tore up the front fender and mirror. Had a wheel stud break once and the front wheel started to come loose and off, lucky on gravel not to fast and stopped. Ruined the wheel holes wallowed out and had to press another stud into the hub that week. Junkyard steel wheel spare was called for. It was a shaky breaky ride for a few seconds. I have never forgot that feeling even 45 years later. LOL

DangFoo

I don't want to get into semantics, as I respect that definition of death wobble may vary, but I doubt it's DW at the rear of your truck. DW is usually associated with the front end; can be associated with the track bar and wallowing out of the mounts (i.e. the holes that allow the track bar to be mounted get widened from a circle to an oval and allow too much play). This is a very common problem on the front end of solid axle vehicles, such as my Jeep.

Did you go through any mud? I've been wheeling and then get back on the pavement where caked-on mud is stuck to the inside of the wheel, thus causing a very unbalanced feel - rear feels like it's wandering. The only other thing I can think of is a bent rim/wheel that would cause an imbalance and result in rough or vibrating characteristic.

There are a lot more mechanically wise people on here than I, so I'm curious to hear about other possible causes.

papa tiger

Last thing to check is a bent axle tube ( Leaking ) as it could do things and being 4x4 ? Even a bent drive shaft ? Use a square up to the box and turn them. No out of round tollerence this way is acceptible.

Scottbell03

I had a similar thing happen to me but not only at 60mph. Mine would happen at random times but over 35 mph. I took it to a dealer because I had rear end work done weeks before and they looked into it and told me it was the E-brake. one of the shoes had busted off and would jam up and cause the horrible wobble. I dunno just a suggestion.