Ok im looking to replace my rear for a posi disc and there is a guy in tucson selling 3 different ones

heres part of the ad:
I've got (3) IROC Z-28 rearends for sale or trade for Chevy performance parts. The first one Part# 10040660 is a Borg Warner 9 Bolt Posi 2:77 equipped with disc brakes. The second one Part# 10032243 is also a Borg Warner 9 Bolt and it has a 3:08 open carrier and is equipped with drum brakes. The third one is a Saginaw Posi 3:73 gears and equipped with disc brakes


I dont think i wanna go to a smaller gear ratio so i was looking at the"saginaw" one but i remember someone saying something about saginaw and not workin but what is saginaw?? I need to know becuase im gonna pick one of these up asap

What would change from me having 3:08 gears(i think) and switching to the 2:77??

Thanks in advance

 

Saginaw is a city in Michigan. Coincidentally, GM had (may still have, I don't know) an axle plant there. The saginaw axle in the ad is most likely a ten bolt 7.5", and is a direct bolt in. The borg warner axles are also direct bolt ins and usually regarded as a stronger rear end. Going from 2.77 from 3.08 will throw the speedo off a little bit (it will read slow) you will accelerate a little slower, and fuel milage will pick up a tiny bit.

Are you going from rear drums to discs?

 

Saginaw is just a fancy way of saying a GM corporate diff (10 bolt).

The 9 bolt never came with 3.08 gears. 2.77, 3.27 and 3.45 are the available factory options for a 9 bolt.

The 2.77 gears are on a 2 series carrier. The 3.27 and 3.45 gears are on a 3 series carrier.

Out of those 3 diffs if the price was the same, I'd suggest the 10 bolt disk with the 3.73 posi but I'd want to open it up and look inside before paying.

 

yeah im gonna need to setup some brake lines and get a prop valve correct? hows my e-brake setup gonna change with this?

 

what exactly should i be looking for that would throw a red flag?

 

a slight correction, you will accelerate faster(you will be running a higher rpm and a larger torque multiplication) and fuel milage will decrease slightly due to the engine running at a higher rpm. thats if you change nothing else though

 

I would also like to know this...
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i would pop the cover off and look see if any teeth are chipped and also make sure it is actually posi and not just welded gears and sorry about my previous post i thought it was going from 2.77 to 3.08 lol

 

i took a look and it just needs some por15, a set of spider gears and some tlc lol its my side project for now any way so i got time to fix it