I have a F85 4-door. I'm having issues figuring out the correct length of the axle shaft. I looked on some websites I found that 2 different ring gear sizes were made an 8.2 and 8.5, and the 8.2 came in two different lengths. Any help? I found the parts on opgi.com.

 

There are good used ones out there also. You have the 8.2, probably the longer ones.