[Bucky1975]

I have what i think is a rear end from an 1980 z28. The #'s on the ring gear are:
GM 3984828 3 40 3 80 . Can some one help me find a web site or more info on my ear end.

[jdcoic]

These two websites have some pretty good info on identifying GM rearends.

http://www.oldsmobility.com/10bolt-tech.htm

http://www.nastyz28.com/camaro/zsusp.html#rearaxle

There should be a set of four #s, something like 15 41 stamped on the ring gear. This will tell you what ratio it is. Just divide the big number by the little one, and that is your ratio. The example above is 2.73

There is also the turn the driveshaft method. Count the number of times you have to turn the driveshaft to make the tire make one revolution, or ten times and divide by 10 (more accurate).

[farna]

If you can see the gears, simply count the teeth to find the ratio. Divide the number of teeth on the ring by the number on the pinion and you have the ratio. The extra numbers on hte ring are the specs used to install the gears originally. Everything will have to be measured again to reinstall them if they've been out or switched to another housing.