I've noticed that my drive shaft is making a very audible clanking noise. I noticed this after a few passes down the track. I placed a camera under my car and saw that my driveshaft is moving up and down probably close to two inches. This is most noticeable if I back into a parking spot then pull forward. I can only imagine how much the rear is moving when I'm launching at the track. I have to investigate my bushings in the rear now and I know very little about IRS ugh. There is even a spot on the shaft when it has made contact with a clip located in the back of the shaft tunnel holding a cable in. I'm assuming is parking brake.