the 1978 to 1987 rear end are them same !

[tybob]

i try to find a rear end 8.5 and i found one from a regal 1978 ! it is the same of a gn 1987 ! ......if not what is the diference ! thay look the same !what kind of car is the same rear end of the tr's (year and model ) thanks

 

[willitell]

All G Body's shared the rearend (7.5" or 8.5"), the only difference was the 8.5 required a different size driveshaft (shorter by 1 inch).

Rearend Swap Tech

 

[tybob]

but the 1978 was a A body or a G body ! some guys say is a A ! that why i ask that question ! ....if the 8.5 1978 have the exact same hosing then the 8.5 1987 tr's , and what is the exact size back plate to back plate of a tr's 8.5 rear ! where i can get the spec ! thanks

 

[willitell]

The 78 and 79 "A Bodys" are the first "G Body" cars. GM changed what the platform was called, not how they built it or what parts they used.

Any how, I beleive you're stuck to looking at later 80s GM cars, specifically the GN, T Type, Hurst/Olds and 442. The monte SS had a 7 5/8s" rear ring. and the others were 7.5. I'm not sure if they even had 8.5s in the A Body cars.


G body.org says-
" First, ALL GM 1981 to 1988 G-Bodies used a 7.5" ring gear rear axle EXCEPT: Monte Carlo SS - 7-5/8" 3.73, Olds 442 - 8.5" 3.73, T-Type and Grand National - 8.5" 3.42 or 3.73. "
Differentials - Code Listing

Hopefully someone else will chime in and verify that i'm giving you the right advice.

 

[HOOGENRAAD]

I think the 84-87 turbo buicks came with the 8.5. Also the 442 olds had the 8.5 also. Hope this helps

 

[kraus]

84-87 hurst and gns used 8.5 78-84 used 7.5's.I have put the 8.5 in a 79 which came out of a 87 gn. There was no difference that I can remember, other then wheels studs were metric on 87 and 79 was not. The only other thing i think was different was the brake lies,not for sure...Reason I know this is because my brother has a stone stock 78 turbo sport coupe which has blown up the 7.5 ,3 times so when we found a 87 gn local we purchased the 8.5 out of it. Hope this helps

 

[tybob]

ok thanks , so if i found one 1978 whit a 8.5 mayby it come from a diferente car ! or is a special order like the tow pacage !thanks your responce help

 

[b4black]

The 1978 8½" may be from a Camaro/Firebird. You don't want that.

 

[88 CuttyClassic]

the complete answer

here is the correct answer in total.. in 1982 the A-body designation changed to G-body. most people get confused because of the sheetmetal change in 81 but the 82 is technically the first car to be called a g-body by GM.. there was no major change underneath from 78-88. Again the only changes were the sheetmetal in 81 and the designation change in 82. As far as the olds cars with 8.5's its the 1984 hurst (not the 83) and the 85-87 442. it was rumored the 88 cutlass GT had 8.5's but this has yet to be proven and only 200 or so cars were ever produced so its dont really matter.

 

[charlief1]

Don't forget that some of the monte carlo ss came with an 8.5" rear end.

 

[b4black]

Don't forget that some of the monte carlo ss came with an 8.5" rear end.

I would disagree with that.

 

[rosewood turbo]

Actualy Ive has 3 SS's over the years and they were 8.5 but non posi and 373 gears.

 

[turbofish38]

Actualy Ive has 3 SS's over the years and they were 8.5 but non posi and 373 gears.

Than somebody other than the factory stuffed them under there. Really if the 8.5 came in Montes than you wouldn't be seeing the 8.5 going for $1000+ in the parts for sale section.MCSSes are a dime a dozen. Over 100,000 of them built in their six years of production. The 83-84 models with the THM350C came with 3.42s. The 85-88 with the 200-4R came with the 3.73. All 7.50s.

Only the 84-87 turbo Buicks and the 84-87 Cutlass H/O-442 came with the 8.5 from the factory as standard equipment.

I'm beginning to think a lot of people cant tell the difference.

 

[turbofish38]

Here are some pics I took because I had the parts on hand.The 7.5 is more square than round and the 8.5 is almost perfectly round.
Pic1 7.50 on the left. 8.50 on the right
Pic2 7.50
Pic3 8.50

 

[b4black]

Good page:
Dorians Diff page!