Toyota Axle Website: http://www.norbie.net/toyotaaxle/
As an example of how to decipher Toyota axle codes:
The '80 Supra from which I grabbed the solid rear axle has code "F312" which corresponds to:
a 7.5" Ring Gear, a 3.909 gear ratio, and 2 pinions with no LSD.
Rob
Copied from celicasupra.com: