I have a 2004 FX4 with around 120,000 miles on it. While pulling my boat, I noticed a very noticeable vibration when taking off. It seem to be worse at a lower speed. I got home, unhooked the boat, and the vibration stopped. I went fishing two more times that week and it happened two more times. Only these times was after the boat was unhooked and going up a small grade. Worse at slower speeds. It only seems to happen when it has been under a load. Any ideas what it could be? How do I determine what it is? Thanks for any input. Also, just had a new tranny put in at Ford.

 

I'm guessing it's an automatic, if the vibration wasn't there before the rebuild take it back with the boat so they can replicate the problem. You might have to tow your boat back home but that would be better than going back and for arguing with the dealer because they can't duplicate the problem.

 

Sounds like a bad U-Joint. Or maybe a cylinder misfire.

 

I thought the same. Will a diagnostic check rule out a misfire if there is no check engine light?

 

I am thinking a bad U-joint

 

There may be a code stored but the light won't usually pop on until the pcm sees the same thing after a run cycle, meaning getting to operating temp from cold twice.

 

If it happens mainly on take off and especially when turning on take off I believe it is most likely your clutch pack in your rear differential.

 

Torx you are correct. I see this concern come into the ford dealer i work at, and i end up replacing the clutch packs pretty often. I suggest trying to make sharp turns at slow speeds and try to power brake while turning. If it is more pronounced, then is the clutch packs.

 

Problem hasn't happened for a while until the other day. I was going down the road and began to feel a slight vibration that gradually got worse. I was running about 45-50 mph when it occurred. After about a half mile of driving it became less noticeable and went away. I tried accelerating and putting the truck in neutral to see if it changed anything, but it did not.

 

What is typical clutch pack change out cost?
Is it something a do-it-yourselfer can do?