What's the quickest and easiest way to tell which gearing I have in my rear end. To my knowledge it's original. 1971 Monte... thank you in advance!

 

run the vin or if you still have the cars info like the book it should give you a better understanding. what engine did it originally come with and also the original transmission it also would give a general idea. with my mercury it came with a tame 4.6 4r70w 8.8 irs but it came with three tame and a getty up and go gears. 1.) 2.63
2.)2.73 (3.)2.83 (4.)3.11 as a last. a true way is to do a gear fluid change on taking the back off and looking at the gear its self or there should be a templet on the door jame saying what general power train could come with for that year