Please help me identify this 12 bolt GM rear end

[jrdamien]

I cannot for the life of me figure it out. There are numbers on the pumpkin but none on the tube.


GM8
k166
707306

The other set of numbers is barely visible but seems to be:

A31122

[1project2many]

Well, that's not a "12 bolt" rear. Looks like a tri-five passenger axle.
The diff case was cast on November 16, 1956.
And you're missing a digit in the part number... Looks like 3707306.
Second number... if it's stamped on side of the case it might indicate the original gear ratio it was assembled with (AB, 3.55 gears, used with Powerglide).
http://www.chevytalk.org/fusionbb/sh...hp?tid/199670/

Also, here's what's called a "12 bolt."


Supporting article: http://www.hemmings.com/hmn/stories/...feature30.html

And here's a "12 bolt truck."

[DransportGarage]

X2. IIRC, that style rear end came in '55-'64 passenger cars. That one's out of a '57 since it was made in Nov. '56.

[DransportGarage]

X2. IIRC, that style rear end came in '55-'64 passenger cars. That one's out of a '57 since it was made in Nov. '56.

Oops. Double post. More coffee...more coffee...

[jrdamien]

Thanks all. Is this a useable rear for a 1/2 ton that's going to be used as a truck with a 235 and a T5?

[1project2many]

Usable? Yes. Good choice? Depends on driving style, how much work you're doing, total power of engine, etc. I'd keep my eyes out for a truck axle. Seems like people are pulling stock frames and powertrains constantly around here. Maybe the "right" one will show up for free.

[DransportGarage]

Originally Posted by jrdamien

Thanks all. Is this a useable rear for a 1/2 ton that's going to be used as a truck with a 235 and a T5?

I don't know what year you're thinking about putting it in, but you might check the wheel flange-to-wheel flange dimension. A '55 3100 is about 61".

I've run that rear end in my '55 sedan since '69 (44 years?????), and it's been a great cruiser. If you're trying to run in the 10s, then I'd go to a 12-bolt or a Currie, etc.

[jrdamien]

Originally Posted by DransportGarage

I don't know what year you're thinking about putting it in, but you might check the wheel flange-to-wheel flange dimension. A '55 3100 is about 61".

I've run that rear end in my '55 sedan since '69 (44 years?????), and it's been a great cruiser. If you're trying to run in the 10s, then I'd go to a 12-bolt or a Currie, etc.

This was actually the rear that came with the frame I bought, so whoever had it was using it with as the rear to their '49 3100.

But I will be carrying and towing with this truck. I want to make sure it's a good option before I get too far.

I also have a '72 Chevelle rear I could use, too.

[1project2many]

But I will be carrying and towing with this truck. I want to make sure it's a good option before I get too far.

I'd probably find a different one.

You've got A 95 1/2 and up 4X4 Tacoma axle would work. They might be cheap in your area, too. The bolt pattern would match the original six lug front, the width is maybe 3/4" different, they're available with 4.10 and 4.56 ratios and a few others less steep that might work depending on which T5 you're using. They're fairly reliable axles and hold up pretty well.

car-part.com is a good place to look for used parts for vehicles less than 25 years old. I checked and there isn't a big supply of 4.10 and 4.56 axles in MN but they're out there. If you start checking other states the prices start dropping and availability goes up. Even with shipping charges, you might be able to find something that's reasonably priced.

[jrdamien]

Since the front is going to be 5 x 4.75 lugs I want the same in the rear, which limits me to Camaro rear ends. Are these Camaro rears that are the favorite for swaps strong enough for a truck that's being used as a light duty truck?

The other option is a Ford rear but then the bolts are still mismatched.

[dwcsr]

Originally Posted by jrdamien

Since the front is going to be 5 x 4.75 lugs I want the same in the rear, which limits me to Camaro rear ends. Are these Camaro rears that are the favorite for swaps strong enough for a truck that's being used as a light duty truck?

The other option is a Ford rear but then the bolts are still mismatched.

S10 4x4 rear works very well. get a 2000 and its a 8.6 with disc brakes

[jrdamien]

Originally Posted by dwcsr

S10 4x4 rear works very well. get a 2000 and its a 8.6 with disc brakes

Is that what you're running? Aren't rear discs without abs prone to locking up? AND...what to do about the bolt pattern?

EDIT: I'm an idiot. CHEVY s10 bolt pattern will be fine. The hunt is on!

[dwcsr]

As long as you use a Disc/Disc master and prop valve you will be ok. You can get one earlier with drum. My understanding is that an 8.6 has disc brakes , 1999 ish up and a 8.5 had drum 1999 ish down. I forgot to say mine was from a 4x4 2000 blazer 2DR ZR2 with the Gov lock option not a pickup.

[jrdamien]

Originally Posted by dwcsr

As long as you use a Disc/Disc master and prop valve you will be ok. You can get one earlier with drum. My understanding is that an 8.6 has disc brakes , 1999 ish up and a 8.5 had drum 1999 ish down. I forgot to say mine was from a 4x4 2000 blazer 2DR ZR2 with the Gov lock option not a pickup.

And how's the fit at 59"?

[dwcsr]

Originally Posted by jrdamien

And how's the fit at 59"?

its 61" thats only 1 " on each side wider