Big shimmy

[westubill]

I am new to this board. Just bought a 74 VW Thing! Good shape, engine strong, very little rust. But, at 45 miles per hour it starts a shimmy that build to near violent shake. I have to practically stop and accelerate from about 10 mph to get it to stop. Hitting bumps also start it off. Everything seems tight when under 45 mph. Any suggestions?
Thanks,
westubill