i want to upgrade my rearend with lower gears & a posi.my code is cca out of a 70 chevelle.i know its a 3.08 non posi.my ? is is this a 8.2 or 8.5 rear or how do i tell the difference?

hey i'm in you exact situation lets see what we hear

If the bolts holding the ring gear in place require an 11/16 wrench then it's an 8.5. If they fit a 9/16 wrench then it's an 8.2. You'll have to pull the cover.

Forgot to mention, check out latest issue of chevy high performance for an article on how to build a tough 10 bolt. Good info on 8.5 vs. 8.2

VERY, VERY probably it's an 8.2. In fact, I'd count on it. Remove the cover and see.

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Tom Parsons

i pulled the cover(2 of them) both 8.2 i read the article.i have to find a 8.5 or 12 bolt thanks for the help

wow, I have never heard the trick about wrench sizes to tell the difference between the 8.2 and 8.5..... this site rules! We should have some sort of reference to all these little tricks someday.. they are a lifesaver.

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Mike Reeh
Gold #34
San Diego, CA

8.5`s have a little square looing ear on each side of the bottom of the center section

8.5's will take a 3/4" wrench on the ring gear bolts, not 11/16.

Another way to tell is the bolt that holds the spider gear pin in. If it takes a 5/16" wrench to remove, it's an 8.5. If its an 8.2, a 1/2" wrench will be the ticket.

I'm gonna agree with DZAUTO that it is almost positively an 8.2.

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70 & 1/2 RS Camaro
SB406 & M20 4spd
9" Rear
70 Malibu
SB350 & TH400

Gold Member # 103
Driveline Technician

If you know for a fact the rear end is 70 vintage then it is an 8.2. 71 is the intro- ductory year for the 8.5. Try looking at Gto Gs 442. They had plenty of chevy 12's loaded under them. Try hooking up with some members from the south or mid-west.Local salvage yards in those areas tend to have loads of older parts than other regions of the USA. Another alternative is the old 9 inch.

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Hey buzz,
I just posted the results of my swap from 3:08 to 3:55. Hopefully will give you an idea of what to expect. It is in the performance section under 3:08 to 3:55 for mb. Hope that helps!

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69'Malibu 350