I put my 04 Kingpin with only 20,000 miles on it, up on the jack, started her up and slipped it into first gear. There is a loud, in conjunction by a softer, banging noise that is not rhythmic . It seems to be coming from under the engine near the transmission. Very clunk, clunk. Also have a clunk when riding and letting off the gas. Any guess as to what this might be? Where do I start?