70 camaro 12 bolt questions?

[2ndgener]

Hears the scoop guys, I have a 70 camaro currently with a 10 bolt with drum brakes. I want to upgrade to a 12 bolt posi and also want to run disc brakes. Also i have aftermarket wheels I put on car and they dont fit quite perfect i would like them to come out just a bit more. I am trying to do this a cheap as possible and strength is not going to be an issue with the horsepower i have at this time. So i was think if I could find a 12 bolt posi out of a pickup that it would prolly be wider so I could take it to the local axle shop and have them cut and weld it up to my desired length. I plan on keeping the leaf springs but may upgrade to the hotchkis tvs kit so the only thing i would have to do is cut brackets off housing and make and weld on new brackets on for springs and shocks right? So if i could find a 12bolt posi out of a pick up with 5 x4 3/4 lug pattern axles and disc brakes i would be hitting a home run right? If the lug pattern is not right i could deal with that just get different axles, but what about the brakes is it easy enough to convert it from drum to disc? I will be thankful for and info i can get as well as any pointers you might have for me, thanks

[chevnut55]

The axles will not matter if your going to have it cut,they will order aftermarket axles with your lugs to fit. i found its also best to clean/smooth the used 12 bolt and mock it up in place and tack weld your brackets, then have the shop weld them on in a jig.

[Randy67]

Pickup 12-bolts are not as strong as the car 12-bolts. Plus trucks had a 5x5 bolt pattern, but this can be changed.

A good cheap upgrade for you would be to get a 71-81 8.5 10-bolt, it's stronger than your 10-bolt and easy to find. You could then use either LS1, C5 or S10 4dr blazer rear brakes for a low cost upgrade. Some of the 79-81s Trans Ams had rear discs as well but are usually pricier to buy.

[2ndgener]

[QUOTE=Randy67;873018]Pickup 12-bolts are not as strong as the car 12-bolts. Plus trucks had a 5x5 bolt pattern, but this can be changed,

So the 12 bolt housings that come out of trucks are different then what came out of cars, that is why they are not as strong?

[2ndgener]

see any problems with the brakes?

[Randy67]

[QUOTE=Randy67;873018]Pickup 12-bolts are not as strong as the car 12-bolts. Plus trucks had a 5x5 bolt pattern, but this can be changed,

So the 12 bolt housings that come out of trucks are different then what came out of cars, that is why they are not as strong?

Smaller diameter pinion (bearings), different gears, and a few other things. Plus more parts available for the car 12-bolt.

[2ndgener]

Are the housings the same tho?

[drc270]

Are the housings the same tho?

they are different

[John Wright]

One more thing to keep in mind besides the track width or overall length of the axle, is the spacing of the leaf spring perches. If they are not spaced the same as your camaro, then you'll end up having to cut them off and reweld them on in the correct location. If you do have to cut/weld the spring perches you also have to pay attention to the pinion angle. It would be money ahead for you to find a similar rear like Randy mentioned. There are some pretty tough 8.5 built these days....may even find one that already has everything on it/in it that you want.

[2ndgener]

found a 8.5 posi out of a 3rd gen camaro with disc brakes on craigslist, does anyone know if the spring perches are the same and the width?

[BonzoHansen]

found a 8.5 posi out of a 3rd gen camaro with disc brakes on craigslist, does anyone know if the spring perches are the same and the width?

3rd gens don't have 8.5s. They have junky 7.5 and are much wider. And the bracketry is all wrong.

Just find an 8.5 out of a 71-81 camaro or firebird and be done with it.

[68vert]

I have a 8.5 10 bolt with 33 spline axles Detroit locked with 3.73 gears I'll be selling soon w/o the baer brakes. It was built by pro-gear in San Diego area. PM me if your interested.

[solarguy09]

I have been running the stock 8.5 10 bolt with the large yokes and tranny output shaft, that are factory GM..

It will take a lot of horsepower and abuse....

But I am talking the 71 Z/28 version, but I am sure they were in other muscle cars.. The regular smaller 10 bolt, no way...

[badazz81z28]

After having done this in the past, (Assuming you have a 8.2 rear),

1. Get an 8.5 10 bolts ALREADY built
2. Buy a Moser 12 bolt

It cost big bucks to get an 8.5 -10 bolt up to par of a 12 bolt. I spent over $1500 on my 10 bolt rebuild. A little bit more I could have saved time and had a better rear.

Don't waste your time "getting other rears" to fit. Buy the correct rearend for your car or go 9"

[NOT A TA]

^^^ X2, Did the whole build a rear thing myself to replace the 8.2 in my car. Should have just ordered a complete rear.

[Skip Fix]

"Just find an 8.5 out of a 71-81 camaro or firebird and be done with it."


Exactly! What are you going to do with the car? My stock 28 spline axled 8.5 rear disc with an Eaton posi has been lots of low 11 and a few high 10 passes on sticky tires.

If you are going to be really hammering on it with sticky tires yes you will need to build it up some. Tires and HP/TQ are the two factors. Street or even road race tires will light up before the thing breaks.