What would cause my van to shake at speeds above 60mph?

Bet breaking in tire, wheel loose, or something in front or rear suspension broken or loose.

u-joint, driveshaft, etc. Anything that rotates that can become "out of balance" If the shaking felt more through the vehicle's body than through the steering wheel check the rear wheels, u-joints, driveshafts, etc.

When did this happen? Do you get free tire rotation and balance? Try that. If you live in the frozen zone, do you have anything frozen on the rims or tires? At highway speeds it may be a wheel bearing going out or the start of tire serration. Have the tires all worn evenly? If not, you may have a tire out of round. If you can tell where, front or back, the vibration is coming from, it will make a difference. Best to have a tire pro look at the tires, rebalanced, and check the wheel bearings. Also make sure all the lug nuts are on and tight.

check your wheel bearings and drive shaft u joints

If the above fails, you may have a cracked fly wheel or a bad crank pulley dampner.

I was driving my 1500 express conversion van an it started binding up on the rear end or driveline what would cause this problem