https://www.google.com/search?q=gra...&es_sm=122&ie=UTF-8#q=grasshopper+mower+parts
Did you purchase OEM Grasshopper belts? You have an expensive piece of equipment and should always replace with original manufacturer parts. Check idler pulleys and spindles for wear, and be sure to grease spindles as well as all grease fittings on mower. My guess is you did not purchase OEM belts at 2 for $25. Mower belts have a different pitch, angle if you will, and much different than automotive belts in order to handle stress, torque, tension, heat, and high rpm's.