A penny weighs about 3 grams. I should've taken a look in the shop to see what the balancing machine looked like. I saw where they took a weight off, put a new one in the same position from front to back, but moved it a few degrees around the radius of the shaft. This second place I took it to is called Bill's Driveshaft in Englewood, CO (with the classy tag line "You can't beat our shafts") and they do a ton of them. When I had my 71 Buick Electra they rebuilt that with a double-carden u-joint drive shaft and did a great job. I noticed the front shaft u-joints were pretty loose and probably need to be done soon. I'll be using these guys from now on for u-joint work.