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Discussion Starter #1
Hi all. I am currently dropping a 500 hp (rough guesstimation) Big Block in my 71 Nova. My question is will a 10 bolt rear end hold up? Im pretty sure mine is a 8.2 inch, but it MAY be a 8.5 inch, with all brand new gears. WIll a 10 bolt hold up to that much power? Also someone told me that it should hold up as long as I use street tires that will be able to spin a little bit before hooking. Can somone please help me with these questions?

Thanks


Rob
 

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rear

If the rear is in overall good condition you will be ok if you are running street tires and a automatic. But remember you can break anything if you try hard enough.... The 8.5 would be a better choice of coarse...

Keith
 

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Discussion Starter #3
Allright. Another thing I forgot to mention is that its a limited slip, not Posi rear end. I dont know if that makes a difference or not though. Im just looking for something that will hold up for a little while until I can replace it with a 12 bolt.

Rob
 

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If its the original rear end it should be a 8.5".....Hot Rod did a story about 8.5" rear ends quite awhile back....said they are good for 650 HP if in good shape and properly prepared....axle tubes welded and such..... my nova...a 74 SS had the 8.5 in it....

good luck
nasty
 

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Being a 71 I would expect that its a 8.2" my self. I agree it will probably live fine on the street assuming you aren't running big slicks and a manual if you wanted a little more beef you could go to the bone yard and grab a 8.5" from a later nova which is very close to the strenth of a 12 bolt for alot less money.
 

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The differential will hold up, but let me tell you what happened to me and my 70 Nova. I had a small block developing probably 350-375hp. On street tires with open headers it would run the quarter in the mid thirteens. After a while the rear axle housing began to rotate off the spring perches. This could be solved by removing the short bolts and replacing them with U bolts that go completely over the housing instead of just through the spring perch. I never broke the rear gears in probably a 100 quarter mile passes.

Vince
 

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8.5" ten bolts showed up in Novas in 1972.

http://www.differentials.com/pdfs/46.pdf this will tell you what rear you have.

The 8.5 is considerably stronger than the 8.2. But 500 horsepower and gobs of torque from the big block will kill both of these rears in stock form, eventually, unless you go fairly easy on them.

Do you plan on doing much drag racing with the car?
 

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Discussion Starter #8
I plan on making MAYBE 1 darg strip trip with the car, just to see what It will run. Besides that its mainly gonna be a street car. Will limited slip increase or decrease the life of the rear end?
 

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Killer if he can't tell the difference by looking at the drastically different 8.2 and 8.5 covers I don't think your link will help, in fact I don't think any link will help him. lol
 

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Discussion Starter #12
Ghetto Jet said:
Killer if he can't tell the difference by looking at the drastically different 8.2 and 8.5 covers I don't think your link will help, in fact I don't think any link will help him. lol

Well that wasn't very nice.. =) By looking at that page it seems the 8.2 inch has a drain plug on the cover. I know mine doesnt, but do they all come like that? And I know its not "oval" shaped which rules out the 7.5 inch rear end. So im guessing its the 8.5 inch rear end. I remember that the plug for putting gear oil in is on the top if the "chunk" area on the passenger side If I remember right.

Guys, im a 20 year old kid thats good at engines and really good at body work/painting, but when it comes to anything else I'll be the first to say Im very ignorant. Just wanted to say thanks for answering the questions I have, even thoguh they may seem "newb" to some of you old veterans.

Rob
 

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if u look at the chevy high performance ad notice the 8.5 , at the lower part of the cover there are ears on the housing.. that is how i check .. an 8.5 can be built to handle up to 1000 hp and higher in some applications.. there are articles that show the 8.5 rear in a light car doing 8's in the quarter mile....
 

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Posi and Positraction are marketing terms for a clutch type limited slip differential that GM produces.

When you say limited slip differential, do you mean open differential? Open is where you do a burn out and you would only spin one tire.

Limited slip is where the slip between the two tires is limited by some means, either clutch and spring, helical gears, viscous coupling, etc...there are many different ways of coming up with limited slip.
 

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Discussion Starter #15
Well I went by my car today which is at the mechanics house. I got under there to look at the rearend and I still cant tell what kind it is. Its definitel not Oval, which rules out the 7 inch rear ends, but it didnt have any "ears" under the bottom, not square ones or pointy ones, so I still don't know what size it is. It didnt have a drain plug in the cover or anything. The only thing that kinda stuck out was that there seemed to be an upside down "V" raised in the cover. I am still stumped at to which rear-end I have.

Rob
 

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RObs71Nova said:
The only thing that kinda stuck out was that there seemed to be an upside down "V" raised in the cover. IRob
V in the cover means it's an 8.2 ten bolt rear. Unless it has 12 bolts in it, then it's a 12bolt passenger car rear.
 

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Ghetto Jet said:
Limited slip decreases the life of the rear, but you'll need it so bad it's not worth worrying about.
I can probably be argued both ways limited slips can help protect parts in situations such as being suck in snow or doing a burn out as it prevents them from turning seperately from the carrier. Spider gears do not live long when one wheel is spun wildly as they have limited lubrication and only flat washers behind them...also keep in mind that assuming one wheel is completely stopped the side gears are going twice the speed the carrier (or speedo) is showing.The trade off is of course that most limited slips do wear in time and either requiring rebuilding or replacing so all in all they do required more maintainance
 

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Helical Gear LSD's require no rebuilding ever. Not good for all out drag applications but ideal for performance mobiles on the street. Typically cost more up front though.
 

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its definitely a 8.2 rear is which i have in my 69 camaro right now..
it holds up ok on the street with about a 500 hp smallblock on slicks.. but at the track it may destroy the rear....

i dont trust it ... so i am replacing it with a fully built to the hilt 8.5 rear .. welded tubes and all....
 

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Look on the passenger side of the rear end on the axle tube and find the vin number for the rear end. The number is usually on the passenger side facing the front of the car or on top of the tube. You can search the internet for rear end numbers. I checked my Firebird and found out from the vin number it was a 8.5 inch 10 bolt with 2.73 gears and no posi. It's easy. You might have to clean some grease and road film to see the numbers but maybe this will help. Good luck.
 
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