Hi everyone just wondering if there is a way to find the ring gear size without taking the diff apart? It's a 79 olds omega 2dr base coupe i put a posi from a 78 in it last year but it was nothing but a headache with constant issues so i put the stock rear diff back in. (replaced leaf springs and changed whole rear end during) I was told by a few ppl that the gearing from a posi 01 S10 rear diff i have laying out back would work in my stock diff just need to confirm the ring gear size. If that's true i'm not positive and honestly not a fan of the gear oil smell lol so the less i am taking the rear end apart the better unless it's a guaranteed fit. I have found 2 different ring gear sizes listed for the car but the body tag codes are not all that legible from time to tell if it's there or not. Any help is appreciated

 

This is a good graphic to help you figure it out.

https://www.novaresource.org/images/rears.jpg

 

7.5 will have 2.5 " diameter tubes...10 bolt 8.5 will be 3" tubes.
Those were the 2 factory rears in the era your in. 1972-1979
If you per-chance have a 10 bolt 8.2 Chevy rear.... The pinion nut will be 1 1/8"
Both the 7.5 and 8.5 have the 1 1/4" pinion nut.