Turner reduction gear is not in diff. If you're looking for a gear reduction for your 500 Daniel Turner will make you one. I just talked to him earlier in week and he will be making them right after Christmas. Cost was either $600. or $650 can't remember right now. I have it written down at my desk.
<a href="http://www.turnercycles.com/" target="_blank">http://www.turnercycles.com/</a>
<a href="http://www.turnercycles.com/" target="_blank">http://www.turnercycles.com/</a>