Will an a-body rearend fit into a g-body?

[70 gsconvt]

Hi, I want to verify if an a-body rearend (8.5 rearend) will fit into a 78-87 g-bodied car. I was told that they did, but wanted to be sure.

Would the rearend need to be modified or can it be just bolted in? Thanks.

[Sportwagon400]

There is a conversion kit to allow it to fit I am not sure who makes it But a friend of mine here has one in his 85 cutlass ( runs 12.0 at 3500 ft!!!! )

Ken

[10sec 455]

Yes, it will fit if you get the conversion arms. The 8.5 rear is a bit wider, hope you dont already have wheels. I think I saw them on Ebay cheap.

[8587GN]

Phil,a friend of mine had two G body 8.5 housings,he lives in Richfield.As of last week he had both of them,he goes by monzaz on here.Send him a pm,or email

[alec296]

southside machine had control arms for that swap
just sold my 12 bolt with the control arms about aweek ago
now running a grand nat 8.5 with all moser inside.girdle,spool
should hold up to major power.
the a body will swap in but shock and spring mounts will very some
and you will have to spread the control arms out from the stock rear
and they will bind so they dont work well that way.
andy

[Randy_W]

I put a '69 Chevelle 12 bolt in my '78 El Camino SS about 25 years ago, the only thing I changed was the u-joint. It worked with no problems for over 5 years. :TU:

[oPh]

Posted this earlier, but its good for a 2nd helping :pp

3 potential problems have to be addressed to propperly fit a '65-72 GM A-body rearend into a '78-80 A-body or '81+ G body.

1st is rearend width.
The '78+ A/G rearends are 52.75" wide (backing plate to backing plate). The '71-72 8.5 A-body rear & '69-72 12 bolt rears are 55.25" wide (bp to bp).
'65-68 12 bolts are 54.25" wide (bp to bp). By doing such a swap, one is moving the tire & wheel combo out either 3/4" or 1.25" per side.
When swapping in either stock width early r/e, tire/wheel clearance @ the outer wheel house lip has to be taken into consideration. Having built dozens of bolt-in axle 8.5 A-body & a few 12 bolt rears for this application, I've yet to run into tire rub when car was running stock wheels & slightly larger than stock size tires. It's when customer already had the wheelhouse "stuffed full", that rear wheels had to be changed to ones with less positive offset.

-Upper control arm geometry, spring & shock location. Without upper control arm mods there will be binding, & the pinion will be up.
Kits like the near $300 Southside Machine swap kit, have been offered to swap the earlier r/e's into '78+ A/G models. One can do a propper fit swap w/o such a kit, by buying or fabbing ones own slightly canted boxed upper control arms, or by purchasing double adjustable uppers like the following:

http://cgi.ebay.com/ebaymotors/G-Body-12-bolt-Swap-Rear-Upper-Double-Adj-Control-Arms_W0QQcmdZViewItemQQcategoryZ33583QQitemZ803684 4822QQrdZ1QQsspagenameZWDVW

One will also need to carefully remove the front hung coil spring locators off the '67-72 A-body rear, & radius the sides of these brackets, then measure & carefully weld them to top of axle tubes. W/o doing so, the rear springs will be sitting at an angle. Stock '78+ A/G body r/e shock mounting is canted. This puts the end of the shock mtg stud dangerously near the section width of really wide tires. 9 times out of 10, @ customers request, I have just left the stock A-body shock perchs as they are, this actually moves the lwr portion of the shock slightly away from wide tires.

-Brake hardware attachment.
If staying rear drums, one will need to use the backing plate from the earlier style r/e. I always throw nice rustfree backing plates in for free on typical A/G swap deal.

Need more info, feel free & drop me an e-mail: resto_services@yahoo.com
:3gears:
Roger

[Randy_W]

Roger, I used my backing plates, I took them off the old rear and never even removed the brake lines. I wired them out of the way and bolt them to the new rear, I thing I had to radius the centers a bit but no big deal. Also not all '78-'80 cars are A-body, my '80 Grand Am that I bought new in Dec. of '79 and sold in Febuary this year, was a G-body as were the Grand Prixs, Cutlass Supremes and Regals as well as Monte Carlos.

[oPh]

Randy,
Hello, the 7.5 A/G body rears are basically the same dimensionally. The 7.5 backing plates I'm aquainted with, have the brakeline go through a golf ball sized hole in the flat steel piece of the housing end of the 7.5 rear. To remove these 7.5 backing plates, one has to remove the line fitting loose from the brake cylinder or just unhook above the rubber hose. Most of the 8.5 A-body swaps I've done, have been in '78 & 79 Elco's as they have been emission exempt in my home state forever. For a longtime, that era of Elco was a hot street/strip build around here, strange but don't see them being built as much anymore.
:3gears:
Roger

[alec296]

i would suggest keeping the 12 bolt backing plates as the wheel cyl bolts
in instead of the clip in g body plates. when the plates get weak
the wheel cyl will twist and shoot past the brake shoe and no brake pedal
andy

[ILLEGAL REGAL]

Southside has been out of business for awhile now, Jegs copied their designs and put them under.

The a-body rear will fit with the conversion arms off ebay and that guy does very nice work. Here's his email... fisher@mo-net.com

[regal8r]

so all u need to get a a body rear end to fit in a g body is get those double adjustable control arms????

[alec296]

get the right control arms and possibly a conversion u-joint/your local
drivline shop should know what you need or maybe someone here online
i think its a spicer 1350? but dont quote me on that. also shaft might need to be shortened. i think you should use the brakes from the a body as wheel
cylinders bolt in rather than clip in.or go with baer rear disc brakes
also you will need different backspace for wheels as rear will be wider than
stock . to fit 28x10.5x15 slicks i had to pound the wheel well 1/4 panel lip
and fold it over .spring perch and shock bolt hole might have to be modified

[oPh]

No conversion u-joint is needed, unless of course one has upgraded to a driveshaft with Spicer 1350 ends, & the rear has 3R pinion flange. Mention that, though whenever I have a build going where a driveshaft with 1350 ujoints is being planned, I''ll order an aftermarket pinion flange to accept the Spicer 1350.

Got Posi?
:3gears:
Roger

[DLG]

Hey guys...

Don't the shocks mount different on the a-bodies?

Just looking at a '75 Malibu and the shocks mount on the forward side of the rearend, and in my g-body they mount on the back....

Am I missing something?

Why doesn't anyone talk about using these 8.5" rears... '73-'77??

[Madcat455]

When I put in the A body rear into my 84 Cutlass... The stock control arms had enough slack to work.

NOW... I don't think the rear end moved like it should've (due to bind like OPh said)... but for street/track use it worked. Had the car running mid 12's... but when I put that drivetrain into my 72 GS... it ran flat 12's with some 11.90's in a heavier car:eek2:

Maybe it was just happy to be "Home"...lol.

I just installed it right as it was... no mods, everything fit. Can't remember if I used the spring perches or not, but I don't think so... I did use them when I swaped into the 72 though (think I reused the 72 perches). NO rear sway bar though, and unboxed LCA's

Definatley had to roll the outer fender lip... but 275/60R15s fit on stock Ttype wheels just fine.

[alec296]

Hey guys...

Don't the shocks mount different on the a-bodies?

Just looking at a '75 Malibu and the shocks mount on the forward side of the rearend, and in my g-body they mount on the back....

Am I missing something?

Why doesn't anyone talk about using these 8.5" rears... '73-'77??

did this,spring perches,shocks, and upper control arms do not match up
and rear end is much wider than a g body.do the a body swap or go 4 link them a 5 in backset for rims just to get them close 8 in rims will need more
you will need to have adjustable arms atleat on top as pinion angle wasnt that good either
i have hear of swaping axle tubes on 8.5 rears with 7.5 g body rears
but the upper control arms will need to be custom and about 2 to 3 inches shorted than stock and offset some

[DLG]

Alec296, you've done this swap before? Does a guy change out the spring perches to what came on the 7.5"? Seems like a lot of hacking since the axle tubes are different diameters.
I could also mod the rear as it is, to put shocks on the back (like the gbody) That I think wouldn't be too hard. Ajustable 'swap' uppers are relatively inexpensive, so I have that covered...

Is the shock location not a problem with other rears?

[stew'86MCSS396]

From what I've been told, the shock location can stay where it is but with the deeper offset rim, there might be some clearance issues with 15" rims. Some have trimmed the bottom of the shock mount by 1/4".

As for the '73-'77 rears, I've seen a thread over on montecarloss.com (well it links you to another) in which it can be done but the way the guy did it, I think you gotta decide if you wanna do it.

http://www.montecarloss.com/community/ubbthreads.php?ubb=showflat&Number=413561&page=0&fpart=1

[alec296]

yes i done the 77 abody to gbody swap
i didnt like it myself as for the problems i listed
if your going that route i suggest a custom suspension like 4 link
or coil over/ladderbar system.
it the mounting thats the problem
it doenst really line up well with stock brackets
you will see when you try it
i suggest the 72 and down abody swap or
take a newer caprice 8.5 rear and have the axle tubes swaped with 7.5
i belive they have the the same tube sizes

[oPh]

There is no reason to use the wrong style (ie, '73-77) A-body housing for this swap, been down that road before w/ several nickel & dime locals & it didn't work out well :(

Use the '71-72 8.5 A-body hsg & follow my earlier directions, & you'll be WAY ahead.



Got Posi?
:3gears:
Roger

[monkeyy337]

I ran a 70 Monte Carlo 12 bolt in my 78 Malibu race car for 8 years using the south side #1328 swap over kit. I used 15X8 Weld wheels with a 5 1/2 inch backspace and ran 275-60-15 Hoosier Quick time tires and Mickey Thompson 11.50X28X15 ET streets and never had to roll a wheel well lip and the tires fit inside the wheel well. I did move the lower spring cups and shock mounts as per the instructions supplied with the South Side lift bars. I also ran an Airbag in the right rear spring. Just my 2 cents worth!