Well, since it's speed related rather than road condition related, and, since it repeats at the same speed range, it has to be something that's turning. Which would lead me to think that you have a bad CV joint or bad wheel bearing. I've also seen a bent wheel act this way. But, a bent wheel would also show up at very low speeds, like less than 5mph. Try letting go of the wheel in a parking lot at about 5-8mph. If the wheel wobbles without your foot on the gas, that would tend to eliminate the CV joint and point more to a bad bearing or wheel.

 

Thanks for your insite.. I have somewhat ruled out the bent wheel as I have switch wheels around front to back ect. and I still get the same shake..I always thought a bad CV joint was noisey with clicking sounds ect when turning sharp turns, say like in a parking lot turning sharp and sort of giving it a little throddle? I have done that in both directions with no noise..

A friend told me that some cars have a big rubber ball like deal on the axle shafts that is supposed to be like a balancer of some sort..He sort of thinks that might be the problem if my van has this balancer thing?

Any other Ideas..Any other ways to test it before buying new CV joints ect? Hate to spend money just guessing and 2 shops I have taken it to have no idea other than maybe try a half shaft..Suppose I could try it but hate to buy the stuff if its not going to fix it..