Excessive vibration after new tire install

I took my 2003 Saturn Vue V6 AWD in and had two new rear tires installed. Immediately after leaving, once I hit 40 MPH I had excessive violent shaking in the steering wheel and whole car. I went back since it felt like either out of balance or loose lug nuts. They checked both and no problem.

Went to my local repairman who does my alignments and he has much more sophisticated balancing equipment. He found them not completely balanced and fixed them.

Problem still existed. We assumed we had bad tires – he replaced them and still same problem. I talked to a mechanic friend and he knew I had just replaced the transmission a month before – he said that sometimes when a transmission is replaced, the CV shafts don’t get seated correctly and that by jacking the car up to change tires, the CV shafts could pull out causing the shaking. We looked and they seem to be fully seated.

Need help figuring out what is causing this shaking. It becomes a harmonic imbalance to where you have to stop the car and start again to have no shaking, but once you get around 35MPH you can feel it starting again. HELP !!!