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Discussion Starter · #1 ·
I still have yet to swap gears in my car, going from 2.92's to a free set 4.11's, I have NO care at all about high rpms on the street, doesnt see much street time. I've heard here and there about the 8.2 10 bolt not being as strong as the 8.5 10 bolt, im sure it is true. What im wanting to know is just what kind of difference im looking at, i have some free stuff, possibly even a locker for the 8.2 (dont forget the free 4.11's), i have a roughly 425hp small block and a 4speed tranny, and im fairly abusive on the clutch, what would be my best bet? put a little money in the 8.2, swap and buy new stuff for an 8.5 (if i can find one), or get a narrowed f..d 9" stuff in some 15 X 10 wheels and slicks for the track and use my regular 15 x 8 for the street ????
 

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In order of my preference: built 8.5, 9". That 8.2 will probably go to pieces on you in a very short time if your drive it hard. We have a built 8.5 in our 72 which has a 495 hp sb in it. 2400 stall converter and 4:56 gears. We welded the tubes to the housing, installed Mark Williams axles and c clip eliminators. We also had the posi unit blueprinted by Tom's Differentials in Paramount Ca. We have had no probs yet. The car runs 10.60's.
 

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The ring gear size has alot to do with the stress the ring gear sees as the pinion tries to climb the ring gear (as the front of the car starts to lift on take off). It is kinda like a lever. With this said, the 8.5" ring gear is a longer lever than the 8.2" ring gear. A lot less stress is seen on the 8.5" carrier. Now the stock axles in the 8.2 have the same spline count and are actually interchangable with a stock 8.5 housing. From what I've heard the stock 8.2 rear end is good for 350 to 400 horse power. The stock 8.5 will hold for between 450 to 500. These numbers kinda depend on how well the car hooks up and standard trannies tend to be harder on a rear than Automatic trannies. If your going to use a stock rear the 8.5 is much better than the 8.2. If your going to fork out the cash for changing the axle splines, specialty posi carrier, braces, and everything else your probably better off going with after market 9" or 12 bolt due to the cost. Your current engine will probably destroy an 8.2. You need the 8.5 at least at this time, but if you start adding horses to the engine you may want to look at getting an aftermarket 12 bolt from Mosier or such.

Just my .02
 

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Discussion Starter · #5 ·
hypotheticaly speaking: what are my chances of making it last till next summer, taking it to the track every other weekend and the occasional trip on the street? keep in mind i am very abusive with a clutch..... is the cost in upgrading an 8.5 anywhere close to the cost of buying a 12bolt? will the 12 bolt stock hold up? or does it need a little bit of upgrading? ive heard the weak part of the 8.2 is the nose where the pinion gear comes out to meet the driveshaft, heard it likes to snap, is this true? can it be braced if someone who knows how to properly weld cast was to put in some braces, at that point would it hold??? alot of questions, but im trying to weigh EVERY option, speaking of EVERY option, im sure this is not even a possibility, but i have a rear from my 62 chevy II from a few years back, im sure it isnt strong enough but ive never heard anything about it so i figured id ask.... already has something like a 4.10 in it......
 

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The nose of the housing is not a problem. The part thi at is likely to break is the ring & pinion gears or the differential (spider) gears. I doubt that it will last long unless you drive it a little on the easy side. I'm not saying that you can't beat on it a little, but regular drag racing with a manual transmission will probably kill it.
I have built several of the 8.5 Nova rear ends and sold them for $1300 complete with a new 30 spline Eaton posi, new 30 spline axles, new gears and all new bearings. I also weld the axle tubes with nickel wire and sand blast the housing. I don't have any cores to build right now, but I should get some around fall.
 

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Discussion Starter · #7 ·
so...... lets say i run across an 8.5, what are the first things i should do to it to make it more abuse proof...??? most important first...
 

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those axles tubes seperate that easy?? with only 425..i think you would need some really good traction to twist or even seperate a tube..just curious
 

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The 8.5 rear ends have very bad plug welds on them. They don't hold up very well at all. If you go to www.nastyz28.com and read about all of the guys who have twisted the tubes in their 8.5 rear ends you will see what I mean. When the tubes twist it puts the yoke and drive shaft into the bottom of the floor. Makes a real mess. The housing is usually scrap after that.
 

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Discussion Starter · #11 ·
so... welding it together is a MUST, does it need any extra bracing? would upgraded axles be a must as well? or just a really good idea?
 

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The only other bracing that I know of would be to the spring perches. The axle tubes will spin before the stock spring perches will bend, but if you weld the tubes you might as well brace the perches too. Just put some flat pieces of 3/16 sheet metal between the ends of the spring perches and the axle tubes and weld them in place.

As for the axles, the stock 28 spline axles will be the weak link if you build the rest of the rear end correctly. The 28 and 30 spline Eaton posi cost the same, and the 30 spline axles are just $30 more than 28 splines. Chances are that the stock axles will need to be replaced anyway. I have only disassembled 1 of the Nova rear ends lately that had usable axles in it.
 

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Discussion Starter · #13 ·
makes sense, just for kicks if you have a moment, can i get an "itemized" list of parts, (im thinking spool) i truthfully dont care about streetability at all, but im in the dark on whats good in the differential dept. so id like to know a rough price on each part??? and what all would be recommended.....
 

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If it makes any difference at this point in the conversation, I had the 8.2 on my 67 rebuilt and tracked all of the parts/prices I used during the rebuild. It's not exactly stock anymore, except for the case. Everything else has been changed out for better quality aftermarket stuff.

http://www.67chevyii.com/projectlist.htm#differential

Not terribly cheap, but it should handle my car just fine up through 450hp that it may eventually be.

If I wasn't concerned about $$$ and wanted to do it over again, I'd probably build an 8.5" or a 9" next time, but I wanted to retain as much of the original setup as I could safely and keeping the 8.2" made sense.

Hope this was somewhat helpful.
 

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Discussion Starter · #17 ·
Thanks big gear head for the detailed info, but to change in a possible different direction, what all is involved in a 12bolt? does it need upgrading? or can it handle it from the get go? would i maybe be better hunting one down and forking over my wallet? if the 12 bolt is good to go stock then in my opinion it would be worth as much, if not a little more than a completely built 8.5... cause it would be a better starting point............ so... whats the deal with a 12 bolt? does it need upgrading for a 425hp, 4sp, with good traction and an abusive driver? or is it good to go stock????
 

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Discussion Starter · #19 ·
what kind of price range would a good used 12 bolt run?
 

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Discussion Starter · #20 ·
as an after thought.... why from just a '68 or '69 Camaro or '68 to '70 Nova ??? is it a length issue? or is it an issue with them being leaf spring and the others having trailing arm\link arm suspension? ive been planning on doing a ladder bar setup, so, if it is just a suspension issue then it doesnt matter..... just wondering Thanks
 
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