I have a vibration in my seat and pedals at about 70 mph. I've balanced and road force balanced the tires, all in spec, still vibrating. I put the rear on jack stands, took the tires off, drove to 70, still vibrating. Took the drums off, because maybe they got unbalanced, still vibrating. I put brand new u-joints in the front and rear driveshaft, still vibrating. Took the rear driveshaft out and went to 70 on jack stands, no vibration. So I think that rules out motor/trans mounts. So I think I have narrowed it down to either a rear axle bearing going out, an internal diff issue, or a rear driveshaft out of balance. My question is, could I remove the rear driveshaft and road test it in 4x4 high at 70 mph and see if the vibration is present and not have any problems doing that? If the vibration goes away, it's the driveshaft, if not, axle bearings or internal diff issues. If it gives more info, it's an 02 Ranger XLT 4x4 4.0 5 speed auto. There's a flange on the output shaft of the transfer case that the driveshaft bolts to, so I don't have to worry about losing any fluid. Thanks

I'd personally just take my drive shaft to a shop and have it balanced before I went and did what you are suggesting.