After reading up what the autodrive system is here:
Differences between Hydrostatic, Transmatic, and AutoDrive drive systems
My guess would be maybe the belts are starting to get worn (slipping). Might first give them a good look over for any cracks or fraying.
Differences between Hydrostatic, Transmatic, and AutoDrive drive systems
My guess would be maybe the belts are starting to get worn (slipping). Might first give them a good look over for any cracks or fraying.