Intermittent vibrations in steering wheel and seat

So, I've been having a major issue that I need some advice identifying. First off the main issue is the vibrations I get in my seat and steering wheel only noticeable at higher speeds 50-75mph. The thing that throws me off is it only happens on certain roads (dirt roads, slightly bumpy freeway) on perfectly smooth roads theres no vibs at all. I first noticed the issue after spending about 3 days off road hunting in the woods on some pretty rough stuff. I've been chasing this issue for a couple months now and wasted alot of money on it. So far I've replaced wheels, tires, ujoints, carrier bearing, and both axles. Any ideas would be much appreciated.
My truck currently has: 17" raceline scouts, open range AT 285/70r17, JBA UCAs, Rough Country front shocks lifted 2", has air bags on the rear and most everything else is oem. PLEASE HELP!!

 

Does it do it in 4th gear.
Don’t worry about running the truck in 4th gear at 70 mph. It will be ok.
I do it all the time towing.

If it doesn’t do it in 4th gear, it’s likely the torque converter.

 

Thanks alot! I'll check to see if it does always thought it was bad to switch over at higher speeds and don't want to learn the hard way.

 

Just put it in 4th to start with then you won’t have drop it to 4th.
But it won’t hurt it either way.
If you’re pulling a trailer at 65 mph, and hit a good sized hill, my truck will drop to forth to maintain 65 mph. It does it on its own. (BTW, it’s not good to tow in forth “normally”)
In the picture below, you’ll see the dash says I’m in “D” (5th). But it’s not, the truck dropped down to 4th. (I was up hill pulling a trailer)

Anyways, try it out and let us know what you find.

And for those who are going to say NOT to use 5th for towing, I know this.
The pictures were for “experimental purposes”. Mostly for post, just as this one.

 

For reference, this is 4th at 65 mph.
It won’t hurt the truck

 

OP says he already replaced those……

 

Correct, I should have read more carefully.

 

I miss stuff all the time. No biggie