1) look for an axle ID tag
2) rotate the tire/wheel 1 full turn, count the number of rotations on the pinion
3) pull the cover plate, divide the # of ring gear teeth by the # of pinion gear teeth... or it may be stamped on the ring gear edge
Look at the diff plate:
Specs:
Code Capacity Ratio
43 Open 3200 3.08
41 Open 3200 3.27
42 Open 4.10
46 Open 3.73
45 Open 3200 3.55
D4 Limited Slip 3200 3.73
D2 Limited Slip 4.10
L73 Limited Slip 3.73
L - Limited Slip Differential
C - Conventional Differential