My boyfriends truck recently had the same issue, and it was really bad. We ended up having to replace his tie rods, steering stabilizer, upper and lower ball joints, and not to mention he blew the belts in his front driver BFG. The combination of all those things made for the worst/scariest ride for the last few weeks.

 

My grand mothers neighbor had this issue. He said all he did was, grease the heck outta the u-joint where it meets the rear diff. He also said ford has it to where the shaft slides in and out of the diff a little, make sure to pull it and push it to grease it up well. Look I know it sounds bad, but please NO perverted jokes.

Found this out when mine started to vibrate. Although ford did mine under extended warranty, only way I will buy used, they said the u- joints where bad, ordered new ones, realized drive shaft was un-balanced, while waiting for u-joints they tried balancing the shaft, no luck, shaft was bent bad.

I got the truck back on a Friday, after they had it since Monday. Told me a new shaft was on order. I asked if my truck was good to tow. They said depends what and wear. They said no further than maybe a 2 hour drive and under 2000 pounds. I said good I need to go fishin. The vibration was horrible with the boat, could not drive over 48.

Brought them the truck back Monday replaced shaft, no more vibration. Went back twice for a spark plug Mis fire that felt like the tranny and cats, then went to have bank 1 cat replaced cause they touched the O2 censors with dirty hands, I guess. Popped right up after I got it back from plugs.

Any way I hope y'all figure out this vibration problem. Might be worth looking into the rear hubs and where the diff meets the drive shaft. may just be the tire weight throwing it off if it doesn't vibrate with out them.

 

That's what i'm confused about. What is causing my tire to keep getting out of balance? Basically, what I do know to be a fact is that with the rear end on jack stands, no wheels on and Wifey hitting the gas pedal to 52MPH, ZERO VIBRATION but as soon as I put the wheels back on, VIBRATION at 52mph. Like I said before, there was no vibration after I got them Roadforce Balanced which lasted all of 2 days and then vibe came back so whatever the problem is would keep causing the tires to be out of balanced. 100% sure I don't need new tire or rims becasue the exact proble to the T existed before I purchased new wheels and tires.

 

I wish I could help more. What does the dealer say about te issue? Have they ever looked at it? Better question is do you trust them? Will they even give a response to what you have performed? or do they want you to spend a couple hundred for them to say We don't know?

The only thing I can recommend is change the bearings and gaskets out in the hub of the rear axel (maybe even something in the drum brakes). I would guess it has to be something there, and the extra added weight of a tire that is even 99.5% balanced may be enough to throw a bearing out of place at those RPMs. Harmonic vibration is a funny thing. That may just be the speed when everything vibrates in unison, who knows, that is more of a hypothesis from physics talking then anything.

Good luck and I hope you figure it out soon. I would look in to the hub now if you have checked the tires and wheels twice already.

 

Thanks for the advice. I did go see a buddy at a shop and we put it on the lift and he put a stethoscope to it and low and behold, there was a noise like beans in a coffee can. One of the pads was broken at the bracket that sits into the caliper. It was hitting against the rotor. Haven't fixed it yet because I'm going do do all 4 brakes but ill let everyone know if it fixes my vibration.

 

Cool deal, hope it works.

 

Found my problem,
After having the shafts rebuilt and the rear one balanced (bad shop they should have found this) I found the front yoke on the rear shaft was off center.
Called ford and they told me this could happen because the shafts are multiple piece construction and can twist and get out of position from high torque driving.
Purchased new shaft and truck rides smooth as silk.

 

my truck does the same thing but over 65 mph it starts and comes and goes..gets really frustraiting im watching this thread to c if anything comes up but will be taking my truck to dealer.