My M3W is just passing 1200 miles. Under heavy acceleration from a dead stop I occasionally get a loud "gun shot" noise coming from the rear. It's a single loud bang and then all is normal. I've pulled covers and inspected the rear and cant find anything. I suspect the belt is slipping however when checking it for tension it seems tight, maybe too tight. I get about 1-1.5 inches for deflection and approximately 45 degrees of twist at the center of the belt span. There is no sign of the belt rubbing or snagging and it appears to track true. The belt alignments on the outside of the pulley.
Your feedback is welcome.
