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Post Info TOPIC: 1981 B Body - 1973-1977 A body diff. swap ??


Poncho Master!

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1981 B Body - 1973-1977 A body diff. swap ??


My 1981 Parisienne has a 7.5 rear diff. with 2.41 axle ratio and I'm thinking I would like to find an 8.5 rear diff that would be a bolt in. Somewhere I read that 1973-1977 Chevelle-Monte Carlo etc. rear diff. is a bolt in and I think they were all 8.5 in that era. Anyone know if this is true or is in something I dreamed? Wherever I read/dreamed this it said the 1977 up B body was essentially built on a 1977 A body chassis. Any input is appreciated!! 

Any late model B-body fans here or am I the red headed step child?? LOL

 

Thanks

Randy 



-- Edited by GLHS60 on Sunday 15th of December 2013 03:35:25 PM



-- Edited by GLHS60 on Friday 21st of November 2014 03:19:20 AM

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1981 Parisienne 400



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RE: 1981 B Body- 1973-1977 A body dif.f swap ??


    

 

77 up B-bodies use a "offset' top bar four link system without a Pan hard bar.



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1981 B Body- 1973-1977 A body diff. swap ??


from the internet    probably  B-body site

 

Question was..

Will my stock 7.5" 10 bolt rear end hold up to a 100 horse shot of NOS?

Answer was..

Your rear end will die if you change anything (it is barely adequate for your stock 267 V-8).

Solution was.. 

You need the 8.5" 10 bolt out of a police car.biggrin                                

If you find any boxed lower links grab them as the '94-'96 Impala / Caprice rear is the same all the way back to "77

(if you can find an Impala SS rear that would be your best bet, as it may have a posi rear that cop cars never get).

 

 Carl 1 probably has a 8.5 posi rear out in the Red River Valley   wink



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RE: 1981 B Body- 1973-1977 A body dif.f swap ??


I am pretty sure the 77 and up B bodies also have an 8.5 in some applications. For sure the Olds B bodies of that era do and it should be a direct swap.

And I happen to have new in the package a pair of 94-96 Impala SS rear lower control arms for sale, VERY reasonable to a site member.....

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Carl Stevenson wrote:



And I happen to have new in the package a pair of 94-96 Impala SS rear lower control arms for sale, VERY reasonable to a site member.....


         sweet    love to see a cousin get a deal   biggrinbiggrin



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Poncho Master!

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427carl wrote:

    

 

77 up B-bodies use a "offset' top bar four link system without a Pan hard bar.


I'm pretty sure the 1973-1977 A body Malibu et.c was the same, not like the earlier B Body with the panhard?? 

 

Thanks

Randy



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1981 Parisienne 400



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Carl Stevenson wrote:

I am pretty sure the 77 and up B bodies also have an 8.5 in some applications. For sure the Olds B bodies of that era do and it should be a direct swap.

And I happen to have new in the package a pair of 94-96 Impala SS rear lower control arms for sale, VERY reasonable to a site member.....


I think they did too but seem to be worth $$ and usually have a 5 on 5 bolt circle. 1973-1977 junker A body's seem more plentiful and are always 5 on 4 3/4.  Just dreaming at this point while watching out for a junker. Wish I could remember where I read the chassis were essentially the same.

 

Thanks

Randy



-- Edited by GLHS60 on Sunday 15th of December 2013 11:36:42 PM

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I confirmed for Randy that the 1973-77 A rears will fit his 81 Parisienne. My source was Rick Lightfoot, POCI rep for the 73-77 A body.

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Appreciate the confirmation Bob!! Now I can be on the lookout for a junker like the one in the movie Drive. Next time you are up this way bring your rubber boots if you have time for a trip to Bucks Auto Wreckers.

Thanks
Randy



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My 78 Chev Bel Air has a factory installed 2.73 8.5 inch "buick" rear end. Did the Oshawa assembly plant use what ever parts they had For these base model cars?

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72 luxo wrote:

My 78 Chev Bel Air has a factory installed 2.73 8.5 inch "buick" rear end. Did the Oshawa assembly plant use what ever parts they had For these base model cars?


My neighbor built a 1948 Chevy coupe and put it on a 1984 Impala cop car chassis that has the Buick style 8.5" rear. I'm not sure why some used this style rear but his has the traditional 5 on 4 3/4" Chevy wheel bolt circle like the 7.5" rears. Later cars with the Chevy 8.5" seemed to have the larger 5 on 5" wheel bolt circle. Do you know what wheel bolt circle your 1978 Bel Air has and what engine ??

 

Thanks

Randy



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Bob F wrote:

I confirmed for Randy that the 1973-77 A rears will fit his 81 Parisienne. My source was Rick Lightfoot, POCI rep for the 73-77 A body.


Hey Bob:

Could I ask you another favor please?? If you get a chance, would you ask your A body friend if a 1973-1977

A body transmission crossmember might also fit? Mine has the curved one that is not dual exhaust friendly. I'm not sure if the later A body's with a cat have the curve or not but the early ones without a cat are probably "double hump".

 

Thanks

Randy



-- Edited by GLHS60 on Monday 5th of May 2014 10:43:52 PM

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GLHS60 wrote:
Bob F wrote:

I confirmed for Randy that the 1973-77 A rears will fit his 81 Parisienne. My source was Rick Lightfoot, POCI rep for the 73-77 A body.


Hey Bob:

Could I ask you another favor please?? If you get a chance, would you ask your A body friend if a 1973-1977

A body transmission crossmember might also fit? Mine has the curved one that is not dual exhaust friendly. I'm not sure if the later A body's with a cat have the curve or not but the early ones without a cat are probably "double hump".

 

Thanks

Randy





         Heres a question about dual exhaust crossmember for 81 Olds Delta  (similar to 81 Parisienne?)

 

        Q    1981 Delta dual exhaust crossmember


Does anyone Know of any company that makes dual exhaust trans crossmembers for the B Body?
 
 
      A    

Quote:

Originally Posted by dirttywhiteboy 

Dpoes anyone Know of any company that makes dual exhaust trans cross members for the B Body?

Yeah, GM did. Get the dual exhaust crossmember from a mid-90s Caprice or Impala SS with dual exhaust.

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I have one of those here that would be free but getting it to Alberta would be painful.

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I appreciate the responses Carl and Carl!!

I'll have to figure how to get it shipped!!

Thanks
Randy

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Wagons & Police cars with the 5" bolt circle used a larger version of the 8.5" rear; the 8.75". My 1977 Olds 98 with a 403 used one as well. 2.41 gears.

 

The 7.5" was used with the 2.56 ratio I thought, while the 2.73 with the sixes used an 8.5". Wagons & B02 used 8.75" with the larger 5" bolt circle.



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GLHS60 wrote:

I appreciate the responses Carl and Carl!!

I'll have to figure how to get it shipped!!

Thanks
Randy


         FYI   When I needed cross member for 66 B-Body Carl 3 (Rick Bless his heart)  shipped it to me  Canada Post wink   

          Honest to God  He wrapped it in Saran wrap!!  stuck on a sticker and mailed it    no poop   



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For shipping awkward and heavy stuff, don't overlook the bus. We used to ship big server boxes all over Quebec using Voyageur without any trouble at all. Far cheaper than Puro-much-later

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YUP, SARAN WRAP AND THE BUS.

SOME CRAZY RABBIT FROM SASK. SENT ME A SET OF HEADERS THAT WAY FOR MY '64.biggrin



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CdnGMfan wrote:

Wagons & Police cars with the 5" bolt circle used a larger version of the 8.5" rear; the 8.75". My 1977 Olds 98 with a 403 used one as well. 2.41 gears.

 

The 7.5" was used with the 2.56 ratio I thought, while the 2.73 with the sixes used an 8.5". Wagons & B02 used 8.75" with the larger 5" bolt circle.


I got a print out based on my VIN from a G.M. dealer and this is where I got my 7.5" /  2:41 axle info.  

Saranwrap and the Grey Hound, sounds like a good idea, I'll try and get the courage to ask Carl if he's a "wrapper"!! LOL

 

Thanks

Randy



-- Edited by GLHS60 on Tuesday 6th of May 2014 01:28:50 PM

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GLHS60 wrote:

I got a print out based on my VIN from a G.M. dealer and this is where I got my 7.5" /  2:41 axle info.  


 Randy, I was merely shooting from the hip. I got a chance to dig into the SAE specs filed for the 1978 Caprice. Attached is the table of ratios and which type of axle assembly it was. You were right about the ratio.

78 B-body axles.jpg



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Poncho Master!

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I appreciate you posting the chart, I didn't realize the "big" 10 bolt was 8.75"

I always thought they were still 8.5", but with out c-clips.

I wonder how far back that diff. goes??

It's good to learn something every day!!

Thanks
Randy

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That's 2 things I learned tonight then. I never heard of bigger than an 8.5 in a 77 or newer B body.

Back to the drawing board for me too...

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Carl Stevenson wrote:

That's 2 things I learned tonight then. I never heard of bigger than an 8.5 in a 77 or newer B body.

Back to the drawing board for me too...


 lookee lookee

 

 

Post  GM B-Body Forum on Mon Mar 17, 2014 3:17 pm

Thought i should write something about this odd ball rear end. The GM 8.75" 12 bolt has an 8.75" ring gear mated to the carrier with 12 bolts. Its also called a 10 bolt because the cover has 10 bolts, but this is actually a 12 bolt. I would call it a hybrid, its like the child of a GM 8.5 10 bolt and a GM 8.875 12 bolt. It was used in the mid to late 70's B-Bodies, usually the wagons, or ones equipped with HD options such as towing. This rear end is very strong, but yet it has no aftermarket because it was only produced for a couple of years. Ive only seen two in my whole life, both had 2.41 ratios, and one had posi and the other did not. It came with a 28 or 31 spline axle, and has a 30 spline pinion and 1-1/4" pinion nut, the same specs that the 8.5's have.
The cover looks like this:

Heres one out of a 79 impala sedan


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The rear end you'll need to find is the 10 bolt from a 77-82 chevy caprice or a Pontiac catalina or the preassian in your case. I'm in the USA so for me it's a CAt. But those rear ends are all direct bolt ins & have the correct bolt patteren for the swao to. The Olds & buuic B-bodies have the bigger version of the 10 bolt & you would have to use the rims as they are the 5X5 bolt patteren. But you are correct that those bodies use the 73-77 A-body frames so they will bolt right in. If you want to make your rear stronger to you can weld a plate onto the bottom of the lower control arms & that will make them a lot stronger. Alos once there boxed in you can add a rear stablizer bar then to. Just make sure you put in a spacer so the arm doesn't collapase when you tighten it up.

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