# Do GM 12 & 10 bolt rear ends come a part?



## Daykron (Oct 13, 2020)

I have a chance to buy a 12 bolt posi for very cheap. The length is 63 1/4 " from mounting face to mounting face and 58" between backing plates.

I have a 1970 Lemans with a stock bop 8.2". The track/tread is 60" in the rear. 

I was wondering is there a way to separate the differential of the rear end from the 2 tubes that house the axle shafts, so it is 3 pieces? 

Can you stick different length tubes into the differential to shorten/lengthen it or to use different perches? 

Or maybe cut the very ends off, by the mounting brackets and weld a new mounting bracket on to suit the length that you want?

Do people normally cut the leaf spring perches off and weld the coil spring perches on?

I have wheels that are 9.5" (241.3mm) wide with an offset of 65mm. So I'm wondering since I'll need a 2"-2.5" wheel spacer to fit the wheels in the rear fenders. Could I just use a longer rear end (as long as my perches & mounts are spaced correctly) or would that screw everything up?

Is this something an average person can't do? 

Would the 12 bolt be of any use to me for my car?

Thanks for your time and answers.


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## Old Man Taylor (May 9, 2011)

1. They're not designed to come apart.
2. You can weld it about any way you want.
3. You don't need it if you're not brutalizing your 10 bolt.


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## Daykron (Oct 13, 2020)

Old Man Taylor said:


> 1. They're not designed to come apart.
> 2. You can weld it about any way you want.
> 3. You don't need it if you're not brutalizing your 10 bolt.


Thanks! 

I wouldn't even know. I don't drive my car, it sits in the garage.

I watched a guy narrow a 9" Ford rear end on YouTube. I thought since the 12 bolt posi is only $150, it might be fun and educational for me to try to alter it so it would fit. Well fun and get a good deal on a 12 bolt.

I see everyone else with 12 bolts and I get jealous because I only have 10 and only 1 tire spins (so I'm told)


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## Scott06 (May 6, 2020)

Daykron said:


> Thanks!
> 
> I wouldn't even know. I don't drive my car, it sits in the garage.
> 
> ...


As mentioned unless you are hopped up you dont need a ford 9” or chevy 12 bolt. Sounds like you want a posi unit maybe a gear change to liven it up if it has highway cruiser gears.
also as mentioned you can shorten that 2 bolt to fit if you are relatively experienced welding.

i just got through swaping out the 4.33 s that were in my 65 for a 3.08 posi i got out of a u pull it yard. Not really that difficult if you have some decent tools and access to calipers and a dial indicator.


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## Mine'sa66 (Oct 30, 2019)

Daykron said:


> Thanks!
> 
> I wouldn't even know. I don't drive my car, it sits in the garage.
> 
> ...


If that is an actual passenger car Chevrolet 12 bolt rear end for $150 you should buy it IMMEDIATELY. That is a tiny fraction of it's value. Be accurate on what you're looking at. A 12 bolt carrier, not a BOP rear with 12 bolts in the cover. That is not a "12" bolt rear end.

Just to add info for you. 1 wheel spinning has nothing to do with 10 or 12 bolts. That is positraction. Both 10 and 12 bolt rear ends come with or without positraction. The 10 or 12 bolts refer to how many bolts secure the ring gear. 12 bolts is stronger than 10, that's why a 12 bolt rear end is what you need for severe usage.
You can tell how many bolts secure the ring gear by counting the bolts in the cover, but only on CHEVROLET rears. Many BOP rears have 12 cover bolts but 10 carrier bolts.


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## Daykron (Oct 13, 2020)

Mine'sa66 said:


> If that is an actual passenger car Chevrolet 12 bolt rear end for $150 you should buy it IMMEDIATELY. That is a tiny fraction of it's value. Be accurate on what you're looking at. A 12 bolt carrier, not a BOP rear with 12 bolts in the cover. That is not a "12" bolt rear end.
> 
> Just to add info for you. 1 wheel spinning has nothing to do with 10 or 12 bolts. That is positraction. Both 10 and 12 bolt rear ends come with or without positraction. The 10 or 12 bolts refer to how many bolts secure the ring gear. 12 bolts is stronger than 10, that's why a 12 bolt rear end is what you need for severe usage.
> You can tell how many bolts secure the ring gear by counting the bolts in the cover, but only on CHEVROLET rears. Many BOP rears have 12 cover bolts but 10 carrier bolts.


I believe the truck 12 bolts have a smaller pinion gear bearing too or smaller pinion shaft I don't remember which.

Thanks


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## Mine'sa66 (Oct 30, 2019)

Daykron said:


> I believe the truck 12 bolts have a smaller pinion gear bearing too or smaller pinion shaft I don't remember which.
> 
> Thanks


Yes, truck is another different ball game.
Good luck in your project.


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