My V70 has developed a pretty significant low speed vibration. Yesterday I put it on jackstands and was able to reproduce it. Looking under the car I saw the "torque tube" (aluminum part bolted to the rear differential) vibrating up and down approximately 1/2 inch. I am looking for help in diagnosing the problem so that I can order parts and either repair myself or take to a repair facility. Any help in this matter will be appreciated.

 

Sounds like something is dangerously out of balance and/or something in the driveline may be siezing up. Regarding the former, look for tires or wheels that are out of true.

Get it to a competent tech asap and at least get it diagnosed; then you can determine if it's something you can safely fix, or let the pro do it.