Posi differential ID

Frankie
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Posi differential ID

Postby Frankie » Wed Jan 14, 2009 1:30 am

Hello everyone - new guy here. I have a GM posi differential that I'd like to ID. It has a 12-bolt 40-tooth 3.08 ring gear mounted with 7/16" LH bolts, and accepts 31-spline axles. One end has a "250" casting no. and an I195 date code. The other end also has the "250" and also a lone "3" which I suppose could be the series? I think it is a late '60's Pontiac "big car" unit, but I guess it may also be a '70s Corporate? Any way to tell for sure? Are those two types interchangable?

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monzaz
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Re: Posi differential ID

Postby monzaz » Tue Jan 20, 2009 11:36 pm

Welcome Frankie... Pictures here would help alot. I am sure this is a Pontiac Full size posi unit made by Eaton Corp. will fit the 1967-1970 Bonneville, Catalina, ventura full size cars. If I can get a picture if the back of the ring area of the posi and the inner spider gear cage area that wil lhelp. Jim
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monzaz
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Re: Posi differential ID

Postby monzaz » Tue Jan 20, 2009 11:42 pm

Does it look like any of these? Jim

Does it have 4 spring cage preload system or a 2 spring preload cage system?
Attachments
rears 032.jpg
65 66 67 68 69 70 pontiac 31 spline posi bolt in axle.jpg
12 bolt 31 spline full size car.jpg
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Frankie
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Re: Posi differential ID

Postby Frankie » Wed Jan 21, 2009 7:30 pm

Here's some pics:
Attachments
PontLSc.jpg
PontLSd.jpg
PontLSb.jpg

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monzaz
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Re: Posi differential ID

Postby monzaz » Fri Jan 23, 2009 3:49 pm

Ok, well I would have to say it is a mid 60's Full size pontiac as long as it has bolt in axles and is 31 spline . The newer 1970 -1977 10 bolt covered , 12 bolt gutted posi like this was 31 and 28 and both were c-clip axles. Maybe a few sqeeked buy with the bolt in axle 31 spline in the 70's.

only thing that throws me is the early pontiacs usually used the 2 spring preload that was pictured above...UNless after a certain ratio (3.08 3.23 3.42) they were upgraded to 4 spring preload...OR some one just rebuilt it down the road and upgrade the spring preload cage and spring set-up. They do interchange. Jim
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certifiedtech
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Re: Posi differential ID

Postby certifiedtech » Sun Apr 12, 2009 12:00 pm

hi I just found this site. cause I was looking for info on the 12 bolt carrier you are talking about. I have one that I pulled out of a 1972 Impala (biscayne) Police car. its been sitting for about 20 years . yes it has 31 spline axles, mine is C clip, has on the Web end between the webs 250 , on the other end the numbers were stamped into the carrier , after cleaning and using a marker , I then could read 32250 , across from that is the date code E241, I guess that would be May 24 1971 , 4 springs in it. Im quessing its an Eaton made posi. these units look beefier that the plain chevy 12 bolt. back when I pulled this I did not even realize the cover only had 10 bolts. also I measured the axle shaft spline end and it is 1.375 or so. I wonder what a 12 bolt chevy 30 spline is ?

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monzaz
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Re: Posi differential ID

Postby monzaz » Mon Apr 13, 2009 10:12 am

OK, I am not complete certain of your question...???

The full size carriers that you have with the 10 bolt cover are different than a 30 spline 1965-1972 a-body gm era unit.

Ring gear bolts are a different size 7/16 on yours compared to 3/8 on the 65-72 muscle car era CAR. Impala used the same a-body mid size car posi as the chevelle and camaro till 1970.

1971 The corporate rears came into being... A new full size 12 bolt was made common for HD full size car and wagons and or up scale model full size usually found in Buick, Olds and Pontiac, Cadillac models. early were 31 spline and then later in the late 70's and early 80's the 10 bolt 12 bolts used 28 spline versions of the same posi.

They are designed off the 66-70 pontiac full size rear of that day...but were swicthed from bolt in axles to c-clip axles in the 70's era.

I do not know if this answered any of your questions ...??? if not please try to re-ask and try again with different wording.
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scatalina67
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Re: Posi differential ID

Postby scatalina67 » Mon Feb 15, 2010 2:57 pm

I have a '67 Catalina and am looking for a posi unit and gear set. I currently have a 2.41 gear and open carrier, and haven't had any luck locating a decent gear or posi assembly. Any of you guys have what I'm looking for or know of some resources that might?

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monzaz
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Re: Posi differential ID

Postby monzaz » Wed Feb 17, 2010 9:42 am

QUOTED: 'also I measured the axle shaft spline end and it is 1.375 or so. I wonder what a 12 bolt chevy 30 spline is ?'

ANSWER:
The 12 bolt chevy will be 30 spline NOT 31 as you have.

The standard 12 bolt chevy (with aftermarket support) 1965-1972 will have the same 1.40 axle bearing surface but of course the spline diameter will be slightly smaller as it losses 1 spline in diameter.
Hope that answer that question....different day better rest...:) Jim
The 2 units are NOT inchangeable persay as 12 bolt chevy will have 3/8 bolt ring gear and different ring gear flange offset to mate the ring to the pinion in the housing.

Tahnks for using J D Race.com
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monzaz
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Re: Posi differential ID

Postby monzaz » Wed Feb 17, 2010 9:49 am

scatalina67 wrote:I have a '67 Catalina and am looking for a posi unit and gear set. I currently have a 2.41 gear and open carrier, and haven't had any luck locating a decent gear or posi assembly. Any of you guys have what I'm looking for or know of some resources that might?



We have a few on the shelf: But only 2.56 2.73 2.93 ratio one or 2 posi units depending on the gear choice I have.

posi 2 series units reconditioned are usually 275.00 (2.29 2.41 2.56) 1 in stock
posi 3 series unit reconditioned are usually 299.00 (2.73 2.93 3.08) 1 in stock
posi 4 series unit reconditioned are usually 350.00 (3.23 3.42 & up) out at this time
2.56 is 40.00
2.93 is 65.00
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kenbarls
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Re: Posi differential ID

Postby kenbarls » Thu Feb 24, 2011 11:27 pm

monzaz wrote:Does it look like any of these rebuilt differentials? Jim

Does it have 4 spring cage preload system or a 2 spring preload cage system?



Hey monzaz. Can I know where I could get those Posi differential? I need them, its for my friend.
Last edited by kenbarls on Tue Mar 08, 2011 5:17 pm, edited 1 time in total.

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monzaz
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Re: Posi differential ID

Postby monzaz » Fri Feb 25, 2011 4:32 pm

kenbarls wrote:
monzaz wrote:Does it look like any of these? Jim

Does it have 4 spring cage preload system or a 2 spring preload cage system?



Hey monzaz. Can I know where I could get those Posi differential? I need them, its for my friend.



Not sure I understand the question please reread and try once more...???
I can get you a posi unit carrier.. .
I can get you 3.55 gears for the Pontiac 8.875 1965-1977
I can build you a complete rear differentail totally.

Jim
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