Gear Swap on 12 Bolt Axle

[BruthaMan]

Hey Guys,

Been checking out some gear swap threads this morning, but unable to find an answer to some questions I have.

I have a 12 bolt axle on my 78 SWB with 2:73 gears. We pulled the cover off to check. I'm not very familiar with axles, but trying to determine what I'll need to swap out gears.

I want to go to a 3:73 setup (700r4 going in). I've seen mention somewhere before about swapping "carriers." Would that be necessary with what I have? Or do I just purchase the gears and have the shop do the work?

Also, how do I tell if it has posi-traction? Is that something I can check with the cover off?

Thanks for your advice!

[Adams74Chevy]

Originally Posted by BruthaMan

...
Also, how do I tell if it has posi-traction? Is that something I can check with the cover off?...

The easiest way to tell is have the wheels off the ground, have a buddy hold one wheel while you turn the other, if it's posi it should make you buddy's wheel turn the same direction you are turning yours.

[Twisted78SS]

Take a look here for a breakdown of parts on a 12 bolt truck axle

http://www.ringpinion.com/PartCats.a...fName=GM%2012T

You should find pictures on the site that show you both open carriers and posi units

[BruthaMan]

Thanks guys, that helps a lot!

One last question. What's the highest gear I can run in a case for a 2:73 gear ratio? I think I read somewhere that with that setup, the highest you can go without swapping out the "carrier" (not sure that's right terminology) is a 3:42.