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  1. #1
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    Default Will an a-body rearend fit into a g-body?

    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.
    Phillip Sedlon
    Wadswoth,OH
    1970 GS convertible, 462/200-4R, (4250 lbs with me), 11.86 at 112 mph, 1.59 60'
    1978 Chevy Z28, 350/4-speed, no where near as fast.........yet!

  2. #2

    Default

    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
    Current rides for
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  3. #3
    Join Date
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    Default

    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.

  4. #4
    8587GN's Avatar
    8587GN is offline <------- reassembly time
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    Default

    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
    Keith Falkowski
    87 GN
    71 GS Stage 1 4 speed,[blue GSX clone]

  5. #5

    Default

    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
    Andy bridgeview,il
    65 special v6 daily driver-this needs to go faster
    82 gn clone 455 12.50's on pump, soon trishield 464
    84 gn
    72 skylark convert#2 ,N-25 for sale

  6. #6
    Join Date
    Mar 2006
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    Salisbury, MD
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    97

    Default

    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.

  7. #7
    Join Date
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    Default

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

    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-Bod...spagenameZWDVW

    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

    Roger

  8. #8
    Join Date
    Mar 2006
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    Salisbury, MD
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    Default

    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.

  9. #9
    Join Date
    Apr 2002
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    Bush Country
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    Default

    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.

    Roger

  10. #10

    Default

    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
    Andy bridgeview,il
    65 special v6 daily driver-this needs to go faster
    82 gn clone 455 12.50's on pump, soon trishield 464
    84 gn
    72 skylark convert#2 ,N-25 for sale

  11. #11
    Join Date
    Jul 2005
    Location
    Tinley Park, IL
    Posts
    12

    Default

    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

  12. #12
    Join Date
    Jul 2005
    Location
    lincoln, nebraska
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    Default

    so all u need to get a a body rear end to fit in a g body is get those double adjustable control arms????
    84 Regal, 350-2 swap (taking wayyy too long)
    96 MC Z34, 3.4L DOHC

  13. #13

    Default

    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
    Andy bridgeview,il
    65 special v6 daily driver-this needs to go faster
    82 gn clone 455 12.50's on pump, soon trishield 464
    84 gn
    72 skylark convert#2 ,N-25 for sale

  14. #14
    Join Date
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    Bush Country
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    Default Re: Will an a-body rearend fit into a g-body?

    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?

    Roger

  15. #15
    Join Date
    Mar 2007
    Location
    Saskatchewan
    Posts
    31

    Default Re: Will an a-body rearend fit into a g-body?

    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??

  16. #16
    Join Date
    Feb 2002
    Location
    Cape Coral, FL
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    1,490

    Default Re: Will an a-body rearend fit into a g-body?

    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

    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.
    Jeff


    E-mail

  17. #17

    Default Re: Will an a-body rearend fit into a g-body?

    Quote Originally Posted by DLG View Post
    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
    Andy bridgeview,il
    65 special v6 daily driver-this needs to go faster
    82 gn clone 455 12.50's on pump, soon trishield 464
    84 gn
    72 skylark convert#2 ,N-25 for sale

  18. #18
    Join Date
    Mar 2007
    Location
    Saskatchewan
    Posts
    31

    Default Re: Will an a-body rearend fit into a g-body?

    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?

  19. #19
    Join Date
    Dec 2006
    Posts
    74

    Default Re: Will an a-body rearend fit into a g-body?

    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/communit...page=0&fpart=1

  20. #20

    Default Re: Will an a-body rearend fit into a g-body?

    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
    Andy bridgeview,il
    65 special v6 daily driver-this needs to go faster
    82 gn clone 455 12.50's on pump, soon trishield 464
    84 gn
    72 skylark convert#2 ,N-25 for sale

  21. #21
    Join Date
    Apr 2002
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    Bush Country
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    713

    Default Re: Will an a-body rearend fit into a g-body?

    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?

    Roger

  22. #22
    Join Date
    Jul 2006
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    bowling green, ky
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    Default Re: Will an a-body rearend fit into a g-body?

    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!

 

 

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