bad vibrations

[xfornow]

I just traded my 04 F-250 4x4 for an 05 Excursion 4x4 6.0l and had the dealer swap my wheels/tires off of my truck to the X. (the X has 58k miles and had the original BFG's on it and my tires were pratically new, maybe 8000 miles on them) Now the truck has vibrations around 45mph and intermittently between 45 and 80mph. While the tires/wheels were on the truck they rode smoothly and had no vibrations. They are Michelin LTX M/S 265/70/16 (standard size) load range E. Prior to the tire swap the X was smooth. What would cause them to vibrate now and do you think the tires are the problem?
BTW The rear-end bearings are howling and the dealer is going to "rebuild" (replace bearings) the rear-end for me. Could the vibration be the rear-end getting worse?? It does not sound any worse than before, but I am wondering if that could be the culprit...the steering is fine (no shake transmitted through steering wheel)...any of your expert help is appreciated. Thanks!

[betontheturtle]

pull the wheels and remount them to the X and properly torque with criss/cross pattern 140ftlbs ( I think) see if that helps. Sometimes shops just run the nuts on with the impact and don't square them up.

[xfornow]

Thanks I will try that tomorrow and hopefully that will correct the problem.

[xfornow]

Did the remount...still vibrating. Dealer says next will try roadforce balance. We will do that when they repair the rear-end.

[jhooch]

The rear-end may be the culprit, sounds like you'll know soon.

[xfornow]

Had the rear rebuilt and it is great. The tires were roadforce balanced and I still have the vibration in the seats between 40 & 50 mph. I am going to start playing with tire pressures tomorrow. It looks like alot of you run 40-45 psi to quell vibrations. I will try that. Any more ideas??

[FordxFour]

Did you drive the X before the tires were swapped? How is the alignment. Just Ideas.

Edit: sorry, I re-read your post, you did drive it before the swap.

[sierra6]

My 05 Ex had alignment problems (caster and toe in) that caused the right front to shake at 70 mph. Go get the truck alignment checked.

[tloc357]

Had this same scenario happen to me on my 02 Ex. Same tires as you have. Vibration started right after I bought the tires so I assumed the tires were bad. I replaced the following to no avail.

. front end aligned
. tires road force balanced
. checked rear end and changed out fluids
. new u-joints in drive shaft (helped a little)

The final solution was I replaced the drive shaft with a new oem one. Vibration gone, rides as smooth as silk.

Hope this helps.

[Mountain Cat]

I had a "rumble strip" like vibration at 50 to 60 mph and it drove me nuts. It started this spring and I was told it was my tires. After I had them balanced, and they were off a bit, the vibration continued. I finally inspected my u-joints on my rear driveshaft and they were worn out pretty bad. I replace them and now my Ex rides nice and smooth.

-Brian

[H1449-6]

Sometimes it's a bad tire. Rare, but it happens.