My 2003 bombardier traxter whines when downshifting. It only happens after it is warm and usually when pulling on a hill. This just started this winter when i rode it in deep snow. Took it to the shop and they can't seem to find a problem. They say there is nothing wrong but I know it wasn't doing this before. It only has 350 hours on it and has only been used for weed spraying on my property. Any ideas?