If your chains slapping against anything, it's too slack IMHO. Adjust it to the Suzuki manual specs.
I rode a 85 Honda V65 Sabre (shaft drive) for several years in college, and if memory serves---> the shaft was kinda clunky down-shifting compared to a chain drive, but the chain makes more noise just going down the road.
Other than that I dunno... Without a better reference to what shaft bike you had, or confirming chain/sprockets are in good shape and adjusted right; it's hard to say....