Update... Dealer replaced tires (their cost not Ford) and swapped driveshaft. problem still exists. Dealer has offered to trade in for 3k less than purchase price. Current mileage 2900. Also drove a new identical truck. fx2 ecoboost 3.31 rear end. Same vibration but more subtle. The situation is causing sleep problems, wake with thoughts of a silverado.

 

Update... Last week a Ford Engineer inspected the truck and determined the problem was the pinion angle was about -.5 degrees and should be about -2.0-3.0 They installed shims yesterday to correct the pinion angle and fix the vibration. It made it worse so they removed the shims and say the truck is within specs. ? The dealer is trying hard to resolve the problem. I'm very surprised that Ford says the current condition is within tolerance after attempting a repair only to revert to the original configuration and now says that the vibration is fine. I'm caught between a good dealer and a bad company.

 

Common issue that has been posted in more threads than I can dig up.

I've had 2 F150's, the both vibrate at 55mph. Tires wasn't the issue. Drive shaft wasn't the issue.

I think most of of us live with it, or trade it. Two different dealers said "its the harmonics of the underbody"......

Its more pronounced in a regular cab because of the shorter wheelbase, and the two-piece driveshaft.

Read here of all the people who experience it.

https://www.f150forum.com/f38/2011-2...tabase-137932/

 

Dealer is blowing you off.

 

Update... Well the FX2 is gone. Ford attempted to fix the problem with shims but it only made it worse so they removed the shims and returned the vehicle to me and said 'it's withing spec'. I found Ford Customer Service to be of no use at all. Their system is really heavily stacked against the customer. Basically, if the field Engineer says it's ok your next step is get a lawyer. I was surprised that the Engineer recognized the problem, tried to fix it but failed ,then said it's normal. I would be driving a Toyota or GMC right now if the dealer had not been great to work with and did all they could to assist me in getting a different truck. Although we had some tense moments the dealership has been great. Ford has been terrible. I'm surprised that Ford really wants to have this truck in the marketplace. I believe that this truck will only lead to more unhappy customers. It'll be interesting to run a CarFax on the VIN in a year or two.

 

I was just on the Ford Dealer lot yesterday and was looking at a 2014 SuperCrew Limited Edition. Instead of the one piece aluminum drive shaft like my 13' model SuperCrew with a 145" wheelbase, the 14" model with the same 145" wheelbase has a two piece steel driveshaft with the carrier bearing.

I guess Ford has narrowed the cause of vibrations to be the aluminum driveshafts being too long?

But then again, OP had a STX with a shorter wheelbase.

 

Vibration still exist with a 2 piece driveshaft... My last truck is proof. Ford hasn't narrowed anything down. "its just the harmonics and engineering of the truck", the last dealer told me.

 

2 piece driveshaft with a carrier bearing is more prone to vibrations. get dealer to swap driveshafts with another truck that you have driven that does not vibrate. if this does not work, swap tires and wheels temporarily. do you have 157" wheelbase or a 2 piece driveshaft? seems to be more prevalent on the longer wheelbase trucks.

 

My 2013 with 4200 miles has driveline vibration since the first month (6 months now). Also has a loud clunk that comes and goes when transitting bumps. I got under today after getting it back from the dealer again and when you grip the yoke of the drive shaft you can physically shake the shaft. Unsure if the its the yoke or the output shaft of the transfer case. The draveshaft is a one piece steel. My neighbors 12 Harley 150 with the Aluminum one piece shaft is tight as tight can be when shaken. I think the prioblem is in the transfer case not the driveshafts.

 

Mine vibrated the day i got it home. Much worse at 55. The left side of the rear bed could be seen doing a little dance it shook so bad.
Unfortunately, when I did a test drive, I never achieved the constant 55mph speed to produce the vibration/shake. I would not have purchased the truck if I had noticed it during the test drive.

Worse with the Michelin 18 inch tires and wheels. the second F150 I had did it, but less obvious---it had stock 17 inch steel wheels and hanook tires.

can't tell you how many times I was at the dealer about this.....Force balanced the tires, ended up replacing the tires, greased underneath, said the driveshaft was not out of alignment (but it was the TWO-PIECE driveshaft). Finally said, they were not putting any more service work into the truck for this issue, and it was just the "harmonics" of the underbody of the truck. B/S.

Got rid of both trucks, probably won't purchase another. Drove 2 rams...Smooth as silk on the road, but I didn't want to spend 12,000 to trade, so I paid $2,800, and got a smaller dodge suv. couldn't be happier.

Ford will continue to give you the run-around on the vibration issue if your truck exhibits it..... Good luck!