[80PontiacWagon]

Hello all. I have a question that seems simple enough, just not experienced enough yet to know.

I've been looking into building a 9 inch for my Pontiac Wagon. I browse eBay all the time looking for pieces and every time I come across a case it lists; I assume, a bearing size.

I found an auction that gives the option between a 3.06" or a 3.25" for the case..

My question is, Whats the difference between the two? And is one better than the other?

Sorry if it seems like a dumb question, but I thought i would come here to get the right answers the first time.

Thanks to everyone for all their help. Much appreciated
-80PontiacWagon

[prostreet6t9]

What axle spline are you wanting to use? The 3.25 case is needed when your gonna use 35 spline axles. So If your going to use 28 or 31 the 3.06 case will be just fine.

The sizes are for the carrier Brg O/D.

[big gear head]

Ford used 2 different differential bearings in the 9 inch Ford. They used a small 2 7/8 bearing and the larger 3 1/16 bearing. There seems to be no reason for the different sizes, they even made nodular cases with both small and large bearings. The 3 1/4 inch bearing case is for after market 35 spline and larger differentials and spools. There are no 28 or 31 spline differentials that use these large bearings. If you buy one of these cases then you won't be able to use the 28 or 31 spline differentials.

[80PontiacWagon]

Thanks for the quick replies. I'm going to run 31 spline axles with an auburn posi.

[prostreet6t9]

Originally Posted by 80PontiacWagon

Thanks for the quick replies. I'm going to run 31 spline axles with an auburn posi.

You might take a look at the Yukon Durigrip posi. Its a better unit than the auburn and the Yukon is rebuildable and the Auburn is not.

[big gear head]

I wouldn't put an Auburn in a golf cart. This is just my opinion, but I think they are junk. The Durragrip is a much better unit, but it sometimes requires some clearance grinding in the case to make it fit. I'm trying one in my 427 4 speed Camaro right now and I haven't broke it yet. I've been beating on it pretty hard.

[80PontiacWagon]

Ok. I'll certainly have to look into that Yukon unit. I need something that will hold up to the 496 i put in my wagon. Can't really get on it with the stock 7.5 rear its got now

[SSedan64]

Many of the full size Wagons came with the 8.5" and Posi. What model Wagon do you have?
7.5" or 8.5" ID>>> http://dyeager535.topcities.com/diffid.html

[80PontiacWagon]

Its a 1980 Pontiac Grand Lemans Safari Wagon with a 7.5. i had it all apart just a few months ago to replace the axle bearings and seals... I believe its something like 2.42 gear. open rear end.