The idler-pully spring broke on the mower deck. The local dealer replaced the spring and belt. Ever since, there has been a huming noise coming from the deck after the first 15 minutes of cutting; when the PTO is first engaged, the mower deck sounds fine, and cuts well. However, the humming noise starts after the first five or so minutes of cutting, and gradually builds to a distinctive consitant hum after 15 minutes. The local dealer thinks this is normal. In fact, they lowered the rpms of the mower so the hum was less noticable, but it's still there. Ive cut with this mower for over a year without this noise. I've also cut with other brands and have never experienced this. There is still one year left on the warranty, and it doesn't sound right to me, and Cub cadet has terrible customer service. They treat you like cancer when you call for help directly. You get the impression their service reps are trained on how to ovoid confronting customer's with warranty work. The local rep is stumped. What could this be?