Ok so I have a 2008 F150 Supercrew 4.6L V8 and I took it offroading a couple days back. As soon as I hit the blacktop my truck would vibrate right at 50mph. There is no vibration before 50mph and it continues vibrating after 50mph. I can feel the vibration under my butt (sorry if that's too much info) and the steering wheel and driver side mirror shake. I went and got an oil change, 4 wheel alignment, rotated the tires, and balanced the tires BUT THE VIBRATION IS STILL THERE!!! I've heard it could be transfer linkage, bearings, u-joints, drive shaft, and a ton of other stuff. This has given me such a headache over the past couple days and I want some discussion on what this could be. Also the vibration is LOUD it almost sounds like you're inside a jet taking off and it drowns out every other sound there is.Please please please help me out on this one before I go insane.

 

Check both front and rear u-joints by trying to shake your driveshaft. If it's stiff your u-joints are fine. If it moves around noticably, they need to be replaced. Also, check your bushings in the front. But I'm pretty sure its your u-joints. Which is cheap.

 

Ok for me the key is after 4 wheeling, most of the time either you threw a wheel weight or maybe have some mud stuck to a rim not comming off or stuck inside a wheel bead,..., wash and check... 2nd things to check all u joints etc I think you have a multi section drive line not sure..... next check and make sure you did not break a shock, this sometimes will cause vibrations just as you describe...

 

Last night I got under the truck and put both hands on the driveshaft and shook it back and fourth and the whole truck moved so I don't think it's the u-joints. There doesn't seem to be any noticeable mud behind the tires although like you said there could be mud inside. Also, how would I go about checking for a cracked spring or suspension? My undercarriage is pretty dirty and it might be hard to notice a crack in something

 

clean out all the mud and rocks from offroading and you should be fine.

If you threw a wheel weight, you may need to have your tires rebalanced.

*edit* im dumb and didnt read you whole post, nvm

 

How hard were you off roading?
sounds like you have a bent drive shaft or a u-Joint that is starting to seize up
easy enough to remove the rear drive shaft to inspct the the U- joints ,just make sure you chock the wheels before doing so.

 

I got the tires balances yesterday and that wasn't it and it was ROUGH offroading......nothing but huge rocks and giant hills I got bounced around so much my flowmaster super 44 muffler got detached from my exhaust pipe. We ended up just taking the exhaust pipe off....all the clamps were still there and I ended up getting it welded on the next day so it won't go anywhere anymore but that should give you guys some insight on how hard I was getting bounced around

 

Well fellas I finally found the problem......I jacked up the back of my truck so the rear wheels were off the ground and I started the truck up put it in drive and my friend was looking underneath and said "dude holy **** look at this"......so I got down look underneath and my driveshaft had a hugeeeee dent in it. You didn't even need to give it gas just put it in drive and watch it spin and it had such a big dent it looked like the driveshaft was wobbling.....so tomorrow I will be making calls around to my local junkyards to find a new driveshaft that isn't dented and won't cause my truck to shake like a ****.....thanks for the input guys I appreciate it!!