I've purchased a 91' Spider with 52,000 miles on it with the knowledge that it would need a little bit of work. For the last six years the car sat in a garage. The major issue it had was a loud clunking noise it would make off the line. I immediately turned to the U-joint, found that to be the issue and replaced it. After replacing that, I am now left with two, very soft clunking noises that I cannot explain when the car accelerates off the line. The drive shaft seems solid to me as does the transmission. The car does not make noise at any other time of the trip. There is a good amount of play in the slip differential that seems like it could produce that noise. I wonder, is that just the spider gears and all is well or have the gears in the differential worn away? Though the sound exists, it does not seem menacing, it is quite melodic... Always off the line, always two knocks, doesn't return until I am back accelerating from 0. Thanks for the input.