i have a d6n aly serial number was pushing dirt and all of sudden lost all steering to both sides transmission still works moves ahead and back in all gears i removed floor boards checked linkage and all there and moving properly it is like it is trying to turn but freewheeling or something broken or bypassing ....no evidence in filters and levels are fine and the dozers works properly any ideas
that machine is a differential steer machine. it uses a hydraulic motor to turn a planetary gear set to provide the steering. i have seen a machine or two that the ring gear the diff. steer motor turns came loose and was not turning the planetary gear set. when you turn the tiller handle all that is turning is the hydraulic motor and pinion but no ring gear. you can pull the hydraulic motor up out of the way and then the pinion shaft and that would allow you to see the ring gear and tell if it is just free wheeling. good luck.