What all could cause vibration starting around 50mph and becoming bad at 60mph? This started immediately following a 4x4 excursion a month ago..

There is some undercab damage on the frame crossmember right where the rear driveshaft u-joint (transfer case side) is. I thought it may have been caused by a high-center. However, there doesn't appear to be any damage to the u-joint. I removed the driveshaft for a closer look. There are some scrapes etc but nothing that I would consider causing vibration.

I removed the u-joint. It seems fine.

Is a driveshaft that sensative that a few scratches can cause high speed vibration?

What else might be causing vibration?

Can I re-use the ujoint I just took out if I didnt damage it? It's probably only 6 months old.

I dont see any major problems that might be causing this but I'll be damn if I dont feel vibration when I hit speed. It's kinda like what you feel when you near top speed and your late model starts to feel like it's going to fall apart. But that's not 60mph for me, more like 75.

 

In your case, it may not be the U-joints. If you damaged the crossmember and changed the angle at which the drive shaft sits or knocked off the driveshaft balance weights, I could see that causing a vibration.

 

Looks like all the weights are still on the shaft but I might have it re-balanced.

The best I could describe things was by saying 'crossbrace' It's actually more of a crossbrace on the bed; I believe. Either way, it's not a drivetrain brace.

 

I had something like this, the wheels weren't balanced. That's all.

 

I had this a couple of years ago and it was a bent driveshaft. The Ford dealership misdiagnosed it but a small-shop mechanic got it right. I didn't believe him and he told me to put the rear axle on jackstands, start the engine, put it in gear and observe the run out (wobble) of the driveshaft. Search the internet and you will find the the maximum allowable runout (TIR, Total Indicated Runout) is very small - maybe .010" or so. Mine was about 2mm (.080") by eye. When I saw this I knew I didn't need to crawl under there, remove the rust from a band on the driveshaft, mount a dial indicator and measure the TIR - I knew he was right.

For a very reasonable price he found one in a junkyard in KY (I live in VA), had it shipped here and installed it.

The walls of these modern driveshafts are thin and it doesn't take much to bend them. I never figured out how mine got bent but if you have obvious dents and scratches it must have taken a little abuse and a little abuse may be all that was required.

Good luck.

EDIT TO ADD LINK

https://www.fleet.ford.com/truckBBAS/non-html/Q14.PDF

 

I rock my truck hard.

Maybe I can try the jackstand approach.

Another thing I'm considering is putting on my other set of tires (smaller 31") and see if it's a tire balance issue.

 

similar problem but I also have 35" tires and a 6" lift. I went back to 4 wheelparts to check on it and according to them it is just Ford. You will find a lot of people complaining about that problem all around the forums.

nothing bad but annoying. I whish I could put a steering stabilizer on my truck.

 

If its dinged up and scratched like you said, I'll put my money on the driveshaft.

 

you idiot..

broken frame and all...

bent driveshaft all the way...

along with a bent brain

...zap!

 

How about mud in the tires??? Hasn't everyone seen My cousin Venny?

 

Bent driveshaft. Argh. Anyone got one for me? hehe

 

Time to go junkyarding