I found this posi carrier in a pile of parts and need some help identifying the details. There is no part numbers on the carrier that I can see aside from a PAT. NO. I purchased a posi rear end and discovered that it is the wrong series for me to use the shorter gears that I would like to run with my T56 transmission. I could buy this carrier for $100 and rebuild it but I cannot find information anywhere about it. The bolts holding the ring gear had 11/16 size heads. The numbers on the ring gear are "39 10 GM 665k 0". I understand this to be a 3.90 gear but I am unsure if it is a 8.2 or 8.5. I tried to measure the ring gear with a tape measure since it was the only thing available and it seems to measure at roughly 8.25. Any insight? I cannot seem to get photos to attach due to their size.

I have added the photos the the Attachment Manager. Note: The pinion gear is nowhere to be found either.

NNorton, are you working on a bop or GM 8.5?
Do you have a picture of the cover?

8.2 BOP. Rather than investing into the mods required to use the 8.5 that I purchased, I would rather purchase an 8.2 BOP posi carrier to put in my original rear end. That's what this would be for.

Do you have yours out yet?
As I recall the bop 8.2 should have the bigger ring bolts you described.

Yes I just pulled my carrier to reference as I look at his again and they are the larger 11/16 head bolts for the ring gear. I'm trying to understand the different posi units. The unit in the photos that he has does not have springs visible in the sight opening of the carrier. I should have gotten more photos of the carrier opening. I don't know if it's worth even $100 if the unit needs springs, rebuild kit, ring and pinion, install kit, etc. I see aftermarket units new for less than $400. I was going to double check to verify that his does not have a recessed ridge for c clips before I purchased it as well.

Look at the diff cover, a bop 8.2 will have the "notches" on the sides by the axles, and will not use the "C" clips.
Ron

Right. The unit that I'm looking at is only the carrier. The pinion gear, rear end, and axles are not there.

Here is some more specific information. I am terribly confused with the 8.2 and 8.5 differences and the identification of the mystery posi carrier. I am looking for the most affordable and practical way to upgrade to a posi rear end. I also have the 8.5 rear end that I could potentially use as well. I would prefer to keep the original rear end under the bird just to keep from relocating the leaf perches but I am open to suggestions.

NOTE: All images have captions to explain details.

Here is my rear end that I pulled out of my 1967 Firebird 400.


Here is the date code and number on the housing.


Here is the two letter code. "XC"


This is my open carrier (left) next to the first posi carrier. The carriers appear identical in overall height but the ring gear sits noticeable higher on the posi unit. I could not find any part numbers on that unit.


Then I compared my open carrier to another style posi. The carrier in the middle also seems to be identical in overall height and the ring gear mount seems to be a perfect match. However, that carrier is a 410408N, which decoded to an 8.5.

Here is some additional information about the other potential option. The current carrier in the 8.5 is a veerryyy tall gear at 2.41 so the series of the carrier is not usable for my desired 3.73, 3.90, or 4.11 gearing. The casting on this 8.5 housing was very difficult to read but it appears to be "PS G63038". This is a GM rear end with c clips but I would be replacing the carrier with a BOP unit from the picture above so I could use my BOP axles if I went that route. I just cannot figure out how to tell the differences when the housings and pinion gears for each carrier are not available. The bearings mic'd out the same, the ring gears had a similar fit, and the 28 spline BOP axles fit with all of these units.

Here are the two rear ends. The original rear end from my bird is on the right.


Here is the 8.5 posi unit that I purchased last week. (I didnt know the differences or what to pay attention to like I know now)


Here is the casting from the middle posi carrier that I compared to my open carrier in the last post.

If you are looking for a 8.2 Pontiac posi carrier I have one that had 3.36 gears on it that is in good shape for 400.00 plus shipping. I live in Mound MN. I had it in my 68 Firebird but went to 2.56 gears for the road instead. It worked great when in car.

I'll probably just order a new eaton unit for $500 or just stick with the open if the cost gets to that range. I'm simply trying to identify if any of these divorced carriers are 8.2. The ring gear on the Eaton style from the first photos is date coded 1966 so I would think that it would be an 8.2 but the ring gear sits up much higher than the open carrier pulled from my 8.2 housing.

Remember the 3 carriers on bop rears for different ratios. Both could still be bop and look different because of being targeted for different gear groups.?