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  #1  
Old Oct 11th, 08, 08:22 PM
PDQ 71 PDQ 71 is offline
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Default Posi Unit Identification see Photos

I'm going to Nova Resource now to look up the numbers but can any one tell me if this is an Eaton Posi Unit? Or another type? It's supposed to be an 8.2 from a 66 Nova and I'm wondering if it's an Eaton made for GM????? Is this supposed to be one of the good ones???? vs the spring type? Here's some pic's.





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  #2  
Old Oct 11th, 08, 08:50 PM
Big Dave Big Dave is online now
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Default Re: Posi Unit Identification see Photos

Borg Warner built it. It uses clutch discs just like an Eaton (you have four steels showing on the side oposite the gear).

This is a common differential found in S-10 pick-ups; but of course the S-10 uses an 8.5 inch ring gear.

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  #3  
Old Oct 11th, 08, 09:37 PM
brian oneil brian oneil is online now
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Default Re: Posi Unit Identification see Photos

Ok Dale, if thats a 8.5, which i agree with Big Dave, it wont fit. Now git rid of that 8.2 and find another housing .
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Old Oct 11th, 08, 10:42 PM
Philip Philip is offline
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Default Re: Posi Unit Identification see Photos

Looks like a TRU Trac from 8.5". It is a factory installed Eaton more commonly found in B body, 73 - 77 A bodies and GN Buicks. The only S-10's that have an 8.5 are the V6 Extremes with manual trans and any other model with the manual trans behind a V6. Not real common S-10 models.
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  #5  
Old Oct 11th, 08, 11:42 PM
PDQ 71 PDQ 71 is offline
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Default Re: Posi Unit Identification see Photos

Houston we have a problem. So far two of you have told me that this is an 8.5" carrier. It was sold to me as being an 8.2" that was supposed to have been in a 66 Nova. Here's the ad on Craigs list:

***** 8.2 10 bolt posi carrier********
Reply to: anon-861921492@craigslist.org
Date: 2008-09-30, 11:50PM

10 bolt gm posi carrier in good shape contact

I removed the ring gear from the carrier and every single Grade 9 bolt broke off during removal. I don't know what they put that thing on there with but those babies were not going anywhere. Big Bertha (MAC 1200 lb/ft impact :-)) just snapped them off. Anyway, I measured the ring gear and I'm not sure how to measure it exactly because of it odd shape. The numbers on the ring gear are either 414 or I think it's 41A GM 297 does that help us any???? I am hoping this is actually an 8.2" as I really don't need an 8.5" and won't be able to use it in my 8.2" differential.
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  #6  
Old Oct 12th, 08, 07:22 AM
Philip Philip is offline
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Default Re: Posi Unit Identification see Photos

They probably snapped off because the 8.5" has left hand threads on the ring gear.
A posi for the 8.2 will have the coil springs in the unit. What was the gear ratio installed on the unit?
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  #7  
Old Oct 12th, 08, 09:43 AM
Big Dave Big Dave is online now
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Default Re: Posi Unit Identification see Photos

"Big Bertha" over tightened those bolts till you sheared the heads off. The 8.5" has 7/16" ring gear bolts with 3/4" heads and use left hand threads. The 8.2" will have 3/8" bolts with 9/16" heads.

Measure the ID of the ring gear with a 12" caliper (the ID tangs are short but they should reach up past the taper on the ring gear to get a good reading). Sorry about the S-10 meant to say C-10 or a ten bolt truck rear end is were I find those rear ends.

With your caliper measure the pinion gear OD if it is 1.438", then you have a truck rear end. The car pinion gear should measure 1.626" dia. (don't sweat getting those bolts out if it is a truck rear end, I consider them to be scrap with the exception of the 14 bolt rear end which I consider to be a poor man's Dana 60 with 33 instead of 35 spline axels).

By the way the only other rear end to use the S clip spring is a Ford 8.8" so I am pretty sure you have an 8.5 inch posi which will interchange with a car rear end no problem. You just have to find a housing and a set of gears and a rebuild kit with new bolts (remember they are left hand threaded so hardware bolts won't work).

Big Dave
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  #8  
Old Oct 12th, 08, 12:22 PM
PDQ 71 PDQ 71 is offline
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Default Re: Posi Unit Identification see Photos

Well son of a gun, I had no idea they were LH thread. Once again, inexperience strikes, I don't have a lot of differential experience and didn't think for a second that they were LH thread, thought they were just frozen on there from being so old and corroded in place or something. Crap. I hate when I do stuff like that. I didn't get the pinion gear with it, and the ring gear is worthless by itself, so it's just scrap metal now. Will post my findings after I take some more measurements to make sure if this isn't an 8.2" carrier.
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  #9  
Old Oct 12th, 08, 04:28 PM
Philip Philip is offline
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Default Re: Posi Unit Identification see Photos

Dale you see the big L on the bolt head, whacha think that could mean

There is no chance it is for an 8.2. On the brighter side the 8.5 is a much better rear end and since you now have a posi for one you just need the rest. What is the count on the side gears for the axle spines? It will either be 28 or 30.
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  #10  
Old Oct 12th, 08, 05:21 PM
PDQ 71 PDQ 71 is offline
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Default Re: Posi Unit Identification see Photos

Well Boy Howdy don't I feel pretty Sheepish about now. Yeah if I ever see any bolts with a GREAT BIG FRIGGIN "L" on them I'll certainly know what that means now won't I????? Well I measured the ring gear and it is definately an 8.5" Gear. Sigh.......... Oh well I guess it's time to think about upgrading to an 8.5" maybe although I do have a 12 bolt Truck rear out back I've been considering cleaning up and getting narrowed to this size but then I'll need to find a posi for it too blah, blah, blah....

How can I tell if this is the 2 series posi or a 3 series unit? I know from what I saw on the Eaton site or the Chevy High Performance can't remember where I saw it now, but the 2 series has a thicker gear surface where as the 3 series is thinner. Anybody happen to know the thickness of the 3 series or have one out they could measure? If it's a 2 series then it's basically useless to me unless I wanted to go ProTouring or something. Anyway, more help please we're almost there!!!!!! If I can't use it, it'll just end up on ebay.
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  #11  
Old Oct 12th, 08, 05:25 PM
Philip Philip is offline
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Default Re: Posi Unit Identification see Photos

Look on the ring gear, it should be stamped on there.

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  #12  
Old Oct 12th, 08, 09:17 PM
PDQ 71 PDQ 71 is offline
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Default Re: Posi Unit Identification see Photos

I'll run a wire brush over the ring gear and see if I can find anymore numbers but they weren't nice and clear like those there. I will look again and try to see though.
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  #13  
Old Oct 12th, 08, 09:23 PM
Philip Philip is offline
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Default Re: Posi Unit Identification see Photos

2.41 and 2.56 gears are all that fit on the 2 series carrier. The 2.73 and lower (higher numerically) fit the 3 series carrier. The area where the ring gear installs isn't hicker, but actually cast more twards the center of the unit to compensate for the smaller diameter pinion. If you can not find the numbers, count the teeth. There are only so many combinations and you may get lucky and have a unique count to help ID the carrier.
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  #14  
Old Oct 13th, 08, 12:00 AM
PDQ 71 PDQ 71 is offline
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Default Re: Posi Unit Identification see Photos

Well I cleaned up the ring gear some more and looked it over really good and the numbers are misaligned at the factory when it was manufactured as you can see in the picture compared to the one Phillip posted. Some Dingbat, misaligned the part marking fixture and the machining process cut into part of the numbers and now you can't read all the numbers. I have no idea what the KK may be on there for. There are some more numbers to the right of the 41A in the valley of the gears and to the left of the 297 also in the valley but I can not make them out because there is not enough of them. To the right of the 41 I took out my magnifying glass and it looks like it could either be an 11 or possibly a 17 but I can't tell for sure. If it's an 11 then that's great because that would mean it was a 3:73 gear set but if it's a 17 then bad news that would be 2:41 which was one of the ratios you said Phillip was for the 2 series. The ring gear has 41 teeth and I'm trying to contact the guy I bought this from and see if he can find out how many teeth were on the pinion gear. Why they didn't pull the gears off I don't know because they are no good separate. I did get my exhaust redone today and those flowmasters sound real nice. I still don't have full exhaust just an 18 inch pipe into flowmasters and then some turn outs but it sounds nice. I'll try and put a short video up this week.


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  #15  
Old Oct 13th, 08, 01:14 AM
PDQ 71 PDQ 71 is offline
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Default Re: Posi Unit Identification see Photos

here is a picture of the two carriers side by side from a tech article on Chevy High Performance. The one on the left is the 2 series carrier as it has a wider flange and is offset slightly more. The one on the right is a 3 series carrier to accomodate the thinner gears. Mine looks like it has the thinner flange but it clearly has the larger area between the clutches opening and the flange. My picture is after this one.



Here are 2 pictures of my unit with the Ring Gear removed. Also here's the link to the article on how build a bullet proof 10 bolt. How to build a bulletproof 10 Bolt Posi for Under $400




So looking at these pictures in comparison to my carrier I'd have to say it is probably a 2 series carrier, however all may not be lost because as I recall you can still use a 2 series posi with a spacer to get into the 3 and 4 series gears if I'm not mistaken but I guess that would then become the weak link, but maybe not with 10 7/16" bolts properly torqued down the spacer might not be a problem. Any comments???
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