I'm almost sure that the vibrations, which only happen between idle and going about 25 miles an hour are due to one or both of the 'collars' that center the driveshaft. Looking at the driveshaft, it looks like a hard rubber 'collar' in the second collar - the rear most - looks broken. So - I want some advice about going to the salvage yard and finding both of those collars and putting on my driveshaft. Thanks.