Shaking then Backfire!

I was driving home from work when I could feel the Van shaking from the backside. I thought maybe one of my tires was going bad so I pulled over to check it out. Tires are good.

So I get going on the freeway doing about 60mph. The shaking gets worse as I slow down to the off ramp I here what sounds like fire crackers going off!

Now I'm just tryin to make it home.

Anyone have a clue whats up?

Fix your U-joints.