I've got a bx 2670 that the back transmission cover got busted. I've got a new one but the small gear by the PTO gear seams to be out further than it should be. Does something need to be engaged for it to go in further. The PTO shifter won't engage it to change to use of rear PTO. Seems stuck. About 1/2" out further than it needs to be. Can't get new cover on.