general problems of the 2001 Toyota 4Runner

When driving at 70 mph, the vehicle vibrates on the highway. I have taken the vehicle constantly to the dealership for over two years complaining about this problem and they always told me that nothing was wrong. Today (5/10/14), the mechanic at the dealership put the truck on a rack and ran the car at 45 mph and there was visible vibration coming from the drive shaft and a loud noise that I could never hear from within the vehicle. All this time, I have been driving a vehicle that I was unaware could have snapped apart. The sound cannot be heard in the cabin, so I could not even report that as a problem until today. I purchased three sets of new tires, had shocks and struts replaced, and brake pads to no avail. Finally, after searching the web yesterday, I realized that this is a common problem with other vehicles of the same make and model. I'm not sure if this problem has caused injury to others, but there should be a recall. This could cause a potentially fatal accident if that shaft breaks. I read that for similar models (Toyota and Lexus), the manufacturer replaced the parts under warranty, but nothing for the 4runner. The dealership is charging over $700 for this repair.