I have replaced the speedometer gear twice. The second time, I replaced the speedometer cable as well. I can go about 40-50 miles and it will quit working. I pull the gear and it is worn just enough that it won’t work. It’s not completely chewed up but more worn. I purchased the gear from Tom’s. How do I know if I need a 6 or 7 spline gear? I’m assuming g the one from Tom’s is the wrong one or else I have a bigger issue. Also, the transfer case has recently been rebuilt.