10 Bolt vs 12 Bolt Width

I have a Flint-built 70 GS455 convertible. The rear end is a non-original 12 bolt and the codes indicate it came from a 1972 Chevelle. The 12 bolt drum-to-drum width is supposed to be 62.5 inches according to the Chevy forums and mine measures pretty close to that. I am trying to compute wheel backspacing options, and if my 12 bolt width is same as the 8.2 then I can use same backspace. Does anyone know the drum-to-drum width of the stock 70 Buick 8.2" axle?

 

They are exactly the same.
The 68-72 Chevy rears are the same width as the 66-72 BOP rears.

 

Thanks Brian. I thought that was the case, but needed confirmation to be sure.

 

rear is 61" over all axle flange to axle flange. add drums 1/8" on each side.
62.5 would be more like a 73- 77 rear width. BUT I am sure you doi not have that in there as all the mounting points are wrong.
64-67 CHEVY is 60" same as a camaro
Jim

 

a 64-67 8.2 is skinnier than a 68-72 8.2 or 8,5

 

Yea and no.
The 64-65 BOP rears are narrow like the 64-67 Chevy rears. The BOP rears went to the wider width for 66,and Carrie red through to 1972. Chevy didn’t go to the wider one until 1968.

 

i put a 71/72 bop 8.5 rear in my 66. its a inch wider than the stock 8.2. read below.

https://www.v8buick.com/index.php?threads/1967-skylark-rear-end.191944/

 

When was your 66 built? Some of the early 66’s had the leftover rears from 65,which were narrower.

 

read the thread above brian the 67 had a shorter rear end as well. in 68 they changed to a differnt version of the 8.2 which is a inch wider. in 71 they went to the 8.5. the 73 up 8.5 is different as well.

 

https://www.v8buick.com/index.php?t...rearend-into-a-buick-i-know-its-a-sin.182530/

read this thread as well last few post. buick had a 1 inch wider rear starting in 68.

 

chevy and BOP rears changed widths at different times.
I have seen MANY more 1966 rear wider at 55.25 flange to flange and or 61" over all drum to drum.
Pontiacs advert as WIDE TRACK commercial verify this also. So all the rest of Buick and Olds also received the wider track rears too.
1966- 1972 BOP (bolt in axles) rear were 55.25 (only early models in 66 might have gotten a left over 65 rear .
chevy was 1964 -1967 having the narrower 54.25 / 60" drum to drum. 68-72 CHEVY were 55.25" / 61" over all drum to drum (C-clip rears)

 

Read that

 

So i just went and measured both just now. My 71 rear is a half inch wider than either 66 rear.

 

Im not arguing with anybody here its just that I got a totally different measurement....
I got 12 bolt in the 67 lark when I measured the width at 61.5 drum to drum face IIRC..

For total curiosity Im going to measure mine again.......

 

My 71 was 61.5 as well so. The 8.2s i have are only 61. Not enough to matter.

 

You also have to take in account that the shafts have end play. That’s enough to make them all equal the same width. Measure the actual housing from end to end to end and you will see what I mean. There was a slight variance between housings. These were mass-produced.

 

Everyone is splitting hairs here on this rear end width... Figure out a bigger problem like the country spending too much money on this freaking virus stuff....lol.

3 trillion here 3 trillion there...no big deal....!!! GOD HELP us. TAX everything will make up for it... ITS FRIDAY!!!!
Jim

 

I just measured the wms. Which i mean the brake drums may be the difference. Idk. Only thing it would matter is someone with super wide wheels. Ima measure my lesabre at home. See what i got there just to see.

 

Jim and myself have dealt with these rears long enough to know what years and what styles are narrow and wide. It’s not just a guess.