Yesterday I was taking the scenic route up a long grade going around 70 in overdrive in an empty 6.0. What I noticed was a vibration that was affected with throttle input and speed. I could back out of the throttle and it would go away, get back into it, and it would return. I hit the tow/ haul which made it downshift, and the vibe went away eventhough my speed was the same and pushed the accelerator which gave me more torque and still, the noise and vibe didn't duplicate itself.
The vibe was very noticable, even to the passenger but not problematic, just pronounced.
I isolated the senario. The noise and vibration happend only in overdrive, going around 70, and pushing the go pedal to get up a long grade. The grade was rather steep because coming back down, I didn't have to even touch the accelerator and I still gained speed, I actually had to mildly brake as not to over speed. There was no "% grade" sign.
I've gone 70 in overdrive before, mostly on flat ground though, never demanding 20 psi boost, and I never heard that vibration or felt it before yesterday.
I'm guessing it was something to do with 'demanding torque at speed'. maybe the overdrive gear in the trans??!
I haven't done a search here on the forum for this, yet.

 

I have also experienced this same issue feeling it in the floor of the truck or the accelerator pedal. Never have figured out the cause...although it doesn't seem to be causing any issues. I have an 07 6.0 F350 crew cab short box.

 

Do you have aftermarket exhaust? Down pipe or part of the exhaust pipe could be slightly touching the frame or another component while under load. Engine could be twisting just enough to do this. My 2002 did this. ~Brad

 

Everything's Stock. Exhaust is all stock (for now,except muff delete).
I did a search and found that TBS's are not relevant to my concern as my tires are fine (balanced). I wouldn't want Ford to poke at it, just fix the problem. Right now it's relativly new with no issues other than this weekends' vibration noticed FIRST by my passenger, (eventhough I noticed it too) she mentioned it first. I could also feel it in the go pedal first.
I haven't dug deep into the TBS or this forum to exhaust our resources of information, just wanted to get a feel out there if anyone else has gone through the same thing.
It didn't feel like part rubbing but more like something in the geartrain.
The last thing I want to do is keep it in that "spot" were it vibrates, either get out of the throttle or get past the vibration (if there is such a place) as I only let off the throttle and changed gears.

 

this is a new one on me.. sorry i havent experienced that before, but i'll bump this for you.

 

Im probably way off but I had the same problem on my truck for a little bit, figured out it was one of two things, one of the rubber mounts had worn out on the exhaust and the exhaust was rubbing on the spare tire. This was with the stock exhaust.
I replaced both and she was smooooth again. Just an Idea, hope it helps!

 

Could it be the drive shaft center support bearing? Ther were some issues of the drive shaft vibrating under load with a trailer due to improper shimming.

 

I was just thinking the same thing. That it's the carrier bearing as it's a loooong way back to the differential. I am just a little disappointed as this is not due to mileage, but torque.
Hey! I just realized... I'm ok with that.

 

Just checked the carrier bearing, some shmo installed it ****-eyed.

It's so obvious, looking dead on. I don't think it could be installed more crooked than it is.
Will straighten it out and road test.

 

I have exactly same problem.Started when I added additive,I,m assuming crud got lodged in one of the injectors. only happens in overdrive