Hello my grandmother asked me to post this question regarding her commercial 60 inch Kubota driveshaft. While she was mowing horse pasture today she had it up on 3 inches because it was high grass. When she finished mowing about 2 acres. she noticed darker smoke coming out from the driveshaft. No grass sticks or debris was around it. she is concerned why it would do this and what is going on. The belt was not hot. I appreciate any of your thoughts. thank you