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77gp
Tribal Scout

14 Posts

Posted - 25 Apr 2015 :  5:23:19 PM  Show Profile  Reply with Quote
Hey guys, I thought that the reared under my 77 Grand Prix was a 8.5" 10 bolt but I was disassembling it today and found it has bolt in axles instead of c-clips. Everything I've read previously said that car should have an 8.5 but is it possible that its an 8.2? I thought that the 8.2 was phased out prior to the 77 model year. I do still have the rear from my parts car but I haven't checked that one yet.

77gp
Tribal Scout

14 Posts

Posted - 25 Apr 2015 :  8:11:14 PM  Show Profile  Reply with Quote
Ok, so a quick update. I was reading an article about identifying rearends, and it seems its definitely an 8.5, the article goes on to say that all 8.5s are held together by c-clips but then contradicts itself by having a sidebar about non c-clip 8.5s being offered in 69-72 Grand Prix and Chevelles through 74. I'm going to clean the axle housing and see if I can find a code on it and see if it is original to this car. Now I guess the question becomes, is this a more desirable reared than a c-clip 8.5? As I understand it the main advantage is just that if you break an axle it won't depart the vehicle, are there any other reasons why thus might be better than a standard rear?
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PontiacMatt
Many Ponies

USA
1410 Posts

Posted - 26 Apr 2015 :  02:12:42 AM  Show Profile  Reply with Quote
As I understand it, that's it. Axle retention. C-clip eliminators are an option for guys running c-clip rears to prevent losing an axle and subsequently a wheel during a launch at the track or wherever. Other than making it easier to remove the axle, there are no other benefits that I'm aware of.

Can't advise as to which rear you may have... Good luck, maybe post pics and see if guys here can help? Also see if you can find any numbers or codes stamped into the axle housing. Just ideas.

*72' Pontiac Lemans* - Work in Progress
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67drake
Sitting Duck

Azerbaijan
1501 Posts

Posted - 26 Apr 2015 :  03:18:34 AM  Show Profile  Reply with Quote
Originally posted by 77gp

Ok, so a quick update. I was reading an article about identifying rearends, and it seems its definitely an 8.5, the article goes on to say that all 8.5s are held together by c-clips but then contradicts itself by having a sidebar about non c-clip 8.5s being offered in 69-72 Grand Prix and Chevelles through 74.

An 8.5 can be a C-clip OR bolt in axle depending on body style ,year,or make of car i.e. Chevy vs. Olds

I'm going to clean the axle housing and see if I can find a code on it and see if it is original to this car. Now I guess the question becomes, is this a more desirable reared than a c-clip 8.5? As I understand it the main advantage is just that if you break an axle it won't depart the vehicle, are there any other reasons why thus might be better than a standard rear?

What Matt said.


71' GTO Original 400 M20 3.23 posi
13.95@102.1 MPH on street tires
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cortcomp
Coyote

USA
5338 Posts

Posted - 26 Apr 2015 :  11:09:38 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
There was an 8.5ish rear end that was olds from 67-69, it had a 12 bolt cover but was a 10 bolt ring gear. I don't think you'd find it in anything that late, but people do rear end swaps from whatever to whatever they have lying around.

Reminds me of a story my dad told me from just after high school (him, not me, i was just a twinkle as they say...)

A friend had a lemans or gto or something that had a rear end making noise (probably from driving the speed limit and not doing burn outs, right?). It was an open rear. He went around to the local car rental places and looked underneath until he found a lemans with the posi lube tag. He rented it for a weekend, swapped the rears. Then, they put some oil on the bolts, ran it down some dirt roads to make it look like no one had been under there on the bolts.

They dropped it off on monday and gave the keys back to the counter guy: "Hey, the car was making some weird noises out back, was kind of whining" "ok thanks, we'll take a look"
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RayK
Cochise

USA
925 Posts

Posted - 09 Sep 2015 :  5:44:40 PM  Show Profile  Reply with Quote
The 8.2 rear end as far as I know was done by 1972, which was a changeover year. Some cars had it and some had the 8.5" rear. The 77 GP SHOULD have the 8.5" factory rear end, and if it's got bolt in axles are you sure someone hasn't changed it over to C clip elims already? I've NEVER seen a 73 and later GP with anything except an 8.5" rear end, and I've seen hundreds, and worked on quite a few, and have owned quite a few.

1969 Firebird 461, #62 iron heads, Comp roller, Performer RPM, Q-Jet Turbo 400 w/ Continental converter. GM 8.5" 10 bolt with 3:73 gears.11.50's@ 119+ MPH
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Chicagogoat
Cochise

USA
823 Posts

Posted - 09 Sep 2015 :  9:19:14 PM  Show Profile  Visit Chicagogoat's Homepage  Reply with Quote
As others have suggested, it may just be an 8.5 10 bolt that's modified for aftermarket axles and c-clip elim hubs. When in doubt count pinion splines and measure ring gear diameter to be sure.

Pure Pontiac: learn it, live it, love it!
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