I have a ZEN NOH ZB7001..Great little workhorse tractor, but the 4WD locked up..We looked in the front end gear housing and it was in pieces..Was told that B7100 parts fit my tractor and we found used gear parts from supposedly a B7100 4 WD tractor..When the parts arrived, they were too big, would not fit..Got any idea what I should do and where I can get those parts..Thanks for any help!!!