Experienced a similar issue with my Mahindra 1533H with 16 hours on it. So, the tractor would go forward and reverse just fine. But, the pedal was very hard to push down to get the tractor to go more than 3 mph. After reading this thread, I decided to go check the parking break and it was not engaged and seemed to be working fine. Then, I checked the "cruise control" (the lever that keeps the hydrostatic pedal in one position). The lever was engaged while the tractor was stationary. Released the lever and the tractor works fine.