Jack up the rear and block the front wheels. place the vehicle in 2wd and see if the rear wheels move without resistance when you press the go pedal. I had a BX that someone stomped on the diff lock when the wheels were spinning and it grenaded the rear differential. It would only move in 4wd. What other symptoms did you have prior to this happening? Has the unit been serviced in accordance with the owner's manual? Are you using Super UDT and [AFFILIATE=1, nofollow=true, newwindow=true, title="Kubota"]Kubota[/AFFILIATE] filters on your transmission? Is the transmission case full as well as the Hydro tank under the seat?