Goin V-8

LO< not realy, but that was funny. When you have the time, crawl under the car and see if there is still a tag attached to a rear end cover bolt. scrap away the grease to find one. The ratio is stamped on there.
(Also, not for nothin, changing the rears oil is more likely a good thing to do because it probably has never been done. You can also find the gear ratio stamped on the ring gear. Rotate the wheel to see where it is stamped on the ring.)