I am getting concerned about a thumping/clunking noise coming from the rear and its either the drive shaft or the pumpkin. When i accelerate from a stop or a quick acceleration while rolling i hear and feel a thump/clunk. XJ 650's have that horrible hard shift noise at times and i dont know if this sound is normal. The rear pumpkin has oil... doesn't leak and seems ok. Could the sound and feeling come from the engine and am feeling it in the rear??? Do the knuckles on the shaft go bad?