10 bolt rear end question 8.2 or 8.5 ?? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 09-13-2004, 05:53 PM
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10 bolt rear end question 8.2 or 8.5 ??

Step 1.
I have a 10 bolt non posi rear end out of an 81 TA. I've taken the unit apart and found the axles to have 28 spline axles and the pinion to have 30 splines with a carrier id of (1252981) with 3.08 gears. OK so far every place I've cheecked said this is a corporate 10 bolt used in the mid 70 to early 80s. I'm almost positive the TA was all original and unmolested. I planned on rebuilding and upgrading it to put in my 73 Firebird.
Step 2.
I found a guy advertising on Ebay a GM 8.5 Posi carrier that once had 3.73s from a Nova. My idea was to use the posi with a new set of 8.5 3.42s I just bought.
This is where everything gets to be a mess. So I get the carrier in the mail and look up the casting numbers (ED 30116 PM) and everyplace I look states this is a 8.2 GM carrier used in the late 60s early 70s Camaros, Firebirds and Nova, not a 8.5. So I'm thinking this guy is an idiot for advertising it as an 8.5 or he just ripped me off. So I start looking at the posi a little more and noticed my 28 Spline axles fit right in. I then was able to bolt the 8.5 3.42 gears right up as well. I have not tried putting the whole assemble in the rear end housing but I assume all will work. How do I tell if this carrier is a 8.2 or 8.5. I assumed the 8.2 and 8.5 are ring sizes and wouldn't interchange and that the two used different sized OD bolts. If it is an 8.2 will it work in the 8.5 housing?

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Old 09-13-2004, 07:30 PM
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Looks like the casting number info is incorrect because the 8.2 gears are definetely not able to go on an 8.5 rear housing, I have a 8.2 in a 68 Malibu and it is waaay smaller and lighter duty then the 8.50 corporate rear that comes in the 73 and up gm midsize cars. Seems to me that you lucked out. Go for it!
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Old 09-13-2004, 08:11 PM
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A GM-made 8.5" 28-spline posi carrier will have the number 410408 or 410409 on it. 410408 is for 2.73-up ratios & will fit your 3.08 rear end gears. 410409 is for 2.56-down ratios. The 8.5" & 8.2" axles have the same spline count & diameter on the inner end, and are interchangeable as long as the length is the same.
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Old 09-16-2007, 12:14 AM
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8.5 10 bolt

I have my build sheet for my 71 chevelle right here and it says it's got the G97 2.73 ratio axle option. Being it's a 10 bolt, I wanted a 12 so I looked into it and found out this particular rear end option is just as strong if not stronger than the 12 bolts. So I put the 3.73 gears in it. It's being ran by a new ZZ4 350 small block with aluminum heads, a Demon ZZ4 4 banger carb and a turbo 350 tranny. I have to say, the 3.73's feel real good in that 10 bolt, it's not even that bad on the highway.
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Old 02-29-2008, 10:24 AM
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will it fit

hi i have a 69 chevelle im sure it has a 8.2 i have a possi and gears out of a 8.5 will these interchange or do i find a 8.5 housing and if so what years would fit thanks for your help
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Old 03-01-2008, 11:43 AM
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Does the inside diameter of the ring gear fit tight to the carrier?
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Old 03-02-2008, 08:16 PM
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Quote:
Originally Posted by bad69
hi i have a 69 chevelle im sure it has a 8.2 i have a possi and gears out of a 8.5 will these interchange or do i find a 8.5 housing and if so what years would fit thanks for your help
They won't interchange. What's the casting number on your 8.5" posi carrier?
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