So right around 70mph I get a real bad vibration. I can't narrow it down to a specific area, the whole Jeep vibrates. It's so bad vehicles in the rear view mirror are just a blur. When I drop below 70mph it goes away. I haven't accelerated past 75mph to see if it goes away. Anyone got any ideas what it could be?

First things to check are driveshaft U-Joints and tires for any bad spots or knots on one of them. Tire or tires could be way out of balance and cause this; if not tires, take a good look at U-Joints on driveshaft for wear or loose joint...