vibration

[adams01]

well ive developed a vibration at 40 to 50 mph.its not a fast vibration its more a up and down feeling in the seat.if i accelerate above 50 or let off or brake below 40 it goes away.im thinking driveline u-joints/carrier bearing but ive never had a truck with a carrier bearing before.they all look original at 109,600 miles.would this be a good place to start?
thanks for any tips/advise

[Piraya33]

Have you done anything new to the truck like put a lift or bigger tires on? I have a 6" lift and I have a vibration from 47-49mph. I replaced the carrier bearing and all U-joints on driveshaft and it's still there. I am going to shim my carrier bearing down a little to see if that helps because someone else had luck with it recently.

[adams01]

no truck is stock no lift.except for m/t wheels with stock size tires.i dont know if it did it before wheels and tires because dealer installed them before i bought it.
thats a sharp looking truck you got.

[adams01]

well i changed my carrier bearing and universals but its still there but only on certain roads?im thinkin tire out of balance or a broken belt in it.gonna rotate and see if it moves with it.any other ideas?

[td04ptgt]

My truck just did this. At ab 45 it would bounce a bit. Anything above and below it wouldnt do it. Had a bubble in the sidewall about 6in long. Purchased new tires and no more problems.

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[adams01]

thank you i will check tires there are only 1200 miles on them since i bought the truck.i was thinking tc.but i left off and left it shift and it did it again at lower rpms but same speed.some roads are alot worse and sometimes it dont do it at all.i was reading alot of other ford owners have had this problem also so its just not me.but no definite cure.
thanks again

[bck4more]

X2 tire had i bubble in side wall

[adams01]

im gonna crawl around and check them now.i hope thats all it is.i dont need a bad tire its soon time to haul my coal for the winter.(i put 3,000 in the bed of my 99 250,wonder if i can put 4,000 in my 350?)