look for a tag on the inside of the drivers door, you should find a axle code, G292 or F303 something like that if its a F its a 7.5 inch ring gear, if a G its a 8 inch ring gear then the 1st and 2nd numbers are the gear ratio, the last digit is the size, meaning 4cyl, v6 and /or limited slip or open
example ---- G102 < my truck G=8 inch -- 10=4.37:1 -- 2=4cyl open diff
(this is a code, email me and i can tell you the gear ratio)
