So I was driving along the highway and as I hit 70 to 80 mph, I started feeling a vibration in the car.
Seat of the pants, or side of the door touching me was vibrating different that the car normally does.
If I backed off below 70, it went away.
it wasn't continuous, and it wasn't rythmic, it just popped up every like 15 to 30 seconds.
steering wheel wasn't moving and it didn't seem like the road doing it.
driven that strech a bunch and never seen it before.

I recently changed out the u-joints, but I checked them and they seem fine.

rear wheels seem to be on tight.
I tried moving them and there is some cluncking side to side when I pull push on each side. not sure if that is normal or not.
bad bearings in the front at least make a heck of a racket.
a while back I pulled the axles to put on rear disc brakes, and I greased the bearings, but didn't change them.
not sure what else to look at.

Maybe threw a wheel balance weight.

My Dad had a similar situation happen to him several years back.
He was on I-10 probably running 80-85 MPH (knowing him). He got a sudden vibration that caught his attention, but ignored it for just long enough for the front right tire on his 2007 Ram 3500 4X4 to let loose (read that as disintegrate). Dad is no slouch behind the wheel, but he was really grateful for the wide grassy shoulder that he was suddenly thrust into. He was shaken after that event, and it takes A LOT for him to get that way.
So my point is: It might be a tire letting loose. But regardless of what it turns out to be, don't get too crazy until you figure it out.

Yeah, the tire thing was also a thought, but the last time one went out of balance on me it also loosened the lug nuts first.
got a ping while driving and realized it had broken a lug and loosened the other nuts.

I took the slow way home afterwards just in case and am slowly working through the car to see if I find a smoking gun.
also had plans for new tires anyway.

went through the back and the rear tires today, will probably play around with the fronts and front end tomorrow, but since the steering wheel didn't shake, wasn't even sure if that could be an issue.

I had a similar experience with a new blazer back in 96? or so. I was on a trip to Ca. from Omaha. Picked up a Vibration somewhere in western Ne. Being a new vehicle I wasn't overly concerned but did keep an eye on it. About 50 miles E of Reno THE LR tire blew at 85 MPH as I was passing two semis pulling doubles. Fortunately I was right alongside the cab of the front truck and they suddenly slowed way down allowing me to get to the R shoulder. I guessed at the time the truck in back let the front one know a potential problem was about to happen.
Of course the tire dealer claimed road hazard which was utter BULL---T