I'm normally a reader and not a poster on here but I know you guys have the answer I'm looking for. I recently changed my YJ diff ratios from 3.07's to 4.10s. At 55 mph it threw my speedo off 15 mph. 55=70 according to my GPS. I read your chart on here and it called for a 37 tooth gear (local jeep dealer didnt have a listing for a 37). Mine currently is a 30. A guy that calibrates speedos near me said that I need a 35. Now, I purchased a 39 at my Jeep dealer. Once I got it home i noticed the shaft was too short...It was a special order and they won't let me return it. Before I possibly waste another $92 I was wondering if anybody knew of a part # for the 35 spline with the long shaft ?