I was driving on the highway the other day and found that the truck was really shaking....I was doing about 70mph. when I slowed, it seemed to lessen. The vibration seemed to be at the front of the vehichle. Now, I know I need an alignment and I think I might even have a flat spot in the right front tire (not sure yet though). Anyway, when I went faster to 80mph...it seemed like the vibration shifted to the middle and rear of the vehichle. I was thinking maybe the driveshaft needed to be balanced. I looked under the truck and it looks as though there is a couple of spots where welds (or glue....whatever they use) was holding on a weight. It is also right near the other weights. Does anyone think that this is my problem and I should have the driveshaft balanced? The other question I have is this...I had the front driveshaft replaced....I read that they are supposed to go on the same way they come off....if you spin them you are screwed. How can I tell if it was installed correctly if it was a bone yard replacement off another vehicle?