# 12 bolt swap problems?



## Pontiachris (Oct 30, 2009)

i have a 12 bolt rear out of a chevelle and i want to put it in place of my 8.5 10 bolt in my lemans i dont have the brake setup on the 12 bolt is it possible to use the brakes off the 10 bolt on a 12 bolt and will i run into problems using the same driveshaft, pinion yolk anything like that?


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## Too Many Projects (Nov 15, 2008)

Pontiachris said:


> i have a 12 bolt rear out of a chevelle and i want to put it in place of my 8.5 10 bolt in my lemans i dont have the brake setup on the 12 bolt is it possible to use the brakes off the 10 bolt on a 12 bolt and will i run into problems using the same driveshaft, pinion yolk anything like that?


To be honest, unless you are running a LOT of hp/torque, the 8.5 rear is all you need. It is much stronger than the older 8.2's and is comparable to a 12 bolt in most areas. 
As far as installing it, I'm not sure if the 8.5 backing plates will interchange but I think they will. The brakes from a 8.2 10 bolt are the same. I don't see why they would've changed them for the 8.5. 
I'm quite certain the u-joint caps will be a different size but there are special joints made just for the conversion. I have one in my 70 Chevelle for some reason. Probably because the driveshaft is out of and Olds with a 8.2. The joints on your drive shaft will most likely be the smaller cap too.


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## 66tempestGT (Nov 28, 2009)

be sure to pay close attention to the driveshaft length. learned this one the hard way. i put what i think was an olds rear in my tempest. i had to let the axle drop down some to get the driveshaft in (after buying an adapter u-joint). first drive down the road to "test" the new gear (4.56) i hit a dip running about 90mph (which was maxed out). after what i literaly thought was an explosion i looked in the mirror in time to see my driveshaft bent into a C shape and spinning down the road. also busted the bellhousing on my trans and put some nasty dents in the driveshaft tunnel. oh to be 21 again!


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## PontiacDave (Jun 9, 2009)

66tempestGT is correct.....you absolutely must check how much driveshaft "play" there is....that is how much extra forward and backwards movement it has. I do not believe there is a "perfect" length but I say shoot for around an inch or so of play to help ensure when the suspension is pushed hard it does not bottom out the driveshaft. I installed a 12 bolt in the past from a 1972 Chevelle and it went into a '65 GTO. The 12 bolts yoke stuck out around an inch more forward than the '65 10 bolt. The driveshaft was a pain to install so I ended up having it shortened an inch, got a conversion u-joint, and all was good.


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## Pontiachris (Oct 30, 2009)

thanks for the info i got the rear for free and its a 12 bolt from a 70 ss396 i think hopefully i can get this thing together correctly


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