I got a rear axle from a 1980 Donor car. according to Nastyz28.com it has a 2.53:1 rear axle ratio. I'm planning to change it out to a 3.73 or a 4.10 rear end. The only problem is, I don't know if it is a 7.5 and 8.5. It had a 305 V8, Turbo 350 trans, and like i said a 2.53 "locking" rear axle. I was wondering if anyone knew what size the rear axle was.

 

And no one answers...

 

pretty sure it's an 8.5. sick

 

check out this site
http://www.chevyhiperformance.com/te...ide/index.html

 

MUCH APPRECIATED!!! Thanks

 

Can't you measure the diameter of the ring gear to find out? Not trying to be a smart a$$ but that's what I think I would do. Jeff

 

That would be the most logical choice lol but I want to get the parts so that way I don't have to have everything sitting around waiting for the parts. A.K.A. I'm lazy lol. I think it's an 8.5 as far as that website went, but there is also an 8.2" that was used for the Second Gen.

 

So w/o knowing the gear ratio, how do you find out what series carrier you have?

 

It says above a 2.73 and up. Is that a 3 series or two?

 

You don't have a 3 series and it should be an 8.5" ring gear. If You're going to change it out any way, then pull the rear cover, Count the teeth on the ring gear and the pinion gear and devide the larger number ( ring gear ) by the smaller number ( pinion gear ) and waalah, gear ratio is revealed. It's a good idea for anyone that's unsure and with a new gasket and gear oil, You can get a gear oil change at the same time.