The easiest calculation that can be done without knowing the number of teeth on the drive gear is this. Needed number of driven gear teeth = Current number of driven gear teeth x (car speed as indicated by the speedometer / car speed as indicated by a GPS). The faster you're going when you measure the speeds indicated on the speedo and the GPS, the more accurate the result will be.
How much
oil can I expect to leak out of the C6 when I pull the sending unit out? Being that I'll have to do it twice (once to count the number of existing teeth, and again to install the new driven gear) that could end up being a very messy job. And Redline ATF isn't exactly cheap stuff.
