Have you had a Road force tire balance done?

 

That's a great idea. No I have not. The reason I have isolated it away from the tires, is this vibration occurs intermittently. Some days, it doesn't happen at all. Other days, it's much worse than the norm. What do you think?

I have a significant rear diff leak (I noticed fresh fluid today). Perhaps when I open it this weekend, I will find something...even if I just find it's low and needs refilling.

Thanks! Keep the ideas coming.

 

Wouldnt hurt to just change the fluid and dont forget the friction additive if yours calls for it
Another thought, if all else fails look into a drive shaft balance test

 

Changed the diff fluid today (including friction additive). It looked good (a little dark) and about the right quantity. I will put it on the road tomorrow to see if that helped.

Drive shaft balance test? Another good idea. I will look tomorrow and see if any counterweights might be missing.

Front diff fluid gets changed this week.

 

Wow, sounds like an unbelievable pita.

I just bought an 08 Expedition (realize this is the forum for the previous generation), it has a pretty bad shake in the steering wheel at speeds over 65mph.

I'm praying that a balancing will take care of it but I have crap luck so I'm not holding my breath.

 

Tail shaft sleeve bearing I bet you find excessive playing in the Driveline yolk when you insert it into the transmission

 

Just wondering if you found the fix for yours... my 2013 is doing the same thing. Trying to narrow down the honey-do list for my husband before I tell him about it. Lol.

 

This is an old thread but thought maybe this would help... I have an 06 expy, age difference aside, mine had a vibration at 80 mph and up which I always thought to be my tires or shocks/struts as they do need replaced but turned out that a bad ignition coil (melted with spring rusted apart) caused it to do that. Found it while changing the spark plugs. Weird thing is it never coded, no cel light, no misfire, no nothing. Maybe urs is as simple as new plugs, boots/springs. Good luck