Yea man there should be a axle tag on the rear axle diff cover or 3rd member on one of the bolts. If you still have your owners manual itll tell you what kinda diff you have(open or limited slip) and what kinda gears you have. Thats how i found out what my 86 had. If you dont have your owners manual get the axle code and tell me the code and ill tell you what you have.

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Also theres two axles that could be in in the rear a 9" or an 8.8" i think they dropped the 9" by 89 but anyway, the way to tell them apart is the 9" doesnt have a removeable diff cover and the 8.8 does(the 9" has a removeable 3rd member.) The front is gonna be a dana 44 TTB