Here is the situation... I have a 99 4runner SR5 v6 auto 4×4. i have replaced the calipers & rotors. I have turned the rear drums and had all 4 tires balanced and road force balanced at the dealership. I have a slight vibration (it feels like drive train, not wheels) at 70 mph and up. The vibration does not necessarily get any worse off with the increase speed but remains mostly the same (if it is worse, it is very slight) Once I had 300 lbs (or so) in the back and the vibration was worse but at the same speeds. The dealer is telling me they do not know what the problem is but it will be a lot to find it and fix it. They think it is the drive shaft... Any thoughts Ya’ll???????