$100 12 bolt

[4x4blaze]

Well, earlier today I stumbled upon a 12 bolt rear out of a late 70's K5 for sale for only $100! Looks to be in pretty decent shape as well! I believe it does has the "gov-lock" dif, but im planning on putting a good eaton or auburn differential in it along with moser axles.

I want to build this rear end, paint it, and have it totally ready to go before I put it in the truck. My current 10 bolt has an open dif and I really dont trust it with the 400 horse small block im currently building for my K5. I know 10 bolts can be built to withstand a lot of abuse, but I'd honestly rather start with a bigger and probably better platform. plus the bigger pumpkin looks pretty sweet..... And for $100, I feel like I can't lose.

My question is, is there anything i need to look for on this axle? And have any of you ever had the axle tubes stretched on one of these trucks? The rear axle being narrower than the front has always driven me nuts.... Is there any real benefit to having it narrower?

And laugh at me if you want but this truck is being built as a cruiser / hot rod styled / modernized 80's / basic white girl jeep / mall crawler..... As strange as that may sound I will eventually start a build thread!

Thanks!

 

[454Sub]

The 10 bolt is basically on par with the 12 bolt for strength. Your not gaining anything other than two ring gear bolts.

 

[4x4blaze]

The 10 bolt is basically on par with the 12 bolt for strength.

Ive heard that before.. But then I've also heard people preach 12 bolts over 10 bolts..

 

[handloader90]

I would hold out for a Semi-Float 14 Bolt. 10 bolts, 12 bolts and Dana 44's are all about the same strength wise. Some say the 10 Bolt (front axle) is stronger than the Dana 44.

I've sold 1/2 ton axles in the past, 10 bolt/10 bolt, 10 bolt/12 bolt, Dana 44/12 bolt and can barely get someone to take a set for $150... I believe the most I've sold a set of 1/2 ton axles for is $160 and the only reason it was that much is because I couldn't break a 20 dollar bill at the time for a guy to make it $150.

1/2 ton axles aren't very desirable but then again I don't know what your plan is for the truck.

Another note. You have less chance of grenading a 1/2 ton axle WITHOUT a traction device. I've heard plenty of stories of guys having open diffs in weaker axles and it saving them from blowing up.

Me personally I would hold out for the semi float 14 bolt.

 

[handloader90]

Not sure how far St. Louis is for you but I would be looking into this over the 12 Bolt. Talk the guy down to $250 or so.

Take the money you were gonna spend on Moser axle shafts and get some regular 6 lug axle shafts and 6 lug rotors for this, have it sandblasted and call it good.

 

[4x4blaze]

I would hold out for a Semi-Float 14 Bolt. 10 bolts, 12 bolts and Dana 44's are all about the same strength wise. Some say the 10 Bolt (front axle) is stronger than the Dana 44.

I've sold 1/2 ton axles in the past, 10 bolt/10 bolt, 10 bolt/12 bolt, Dana 44/12 bolt and can barely get someone to take a set for $150... I believe the most I've sold a set of 1/2 ton axles for is $160 and the only reason it was that much is because I couldn't break a 20 dollar bill at the time for a guy to make it $150.

1/2 ton axles aren't very desirable but then again I don't know what your plan is for the truck.

Another note. You have less chance of grenading a 1/2 ton axle WITHOUT a traction device. I've heard plenty of stories of guys having open diffs in weaker axles and it saving them from blowing up.

Me personally I would hold out for the semi float 14 bolt.

Wow, that is not what I expected to hear. Huh.. And thanks for finding those ads! My ultimate goal for this truck is building it as a cruiser.. I want to be able to hop in it and cruise 500 miles without an issue. Not saying that it wont see mild off road conditions here and there, but nothing extreme. And it should be making roughly 400 or so horse, so it will be fun to beat up on newer trucks occasionally... This truck currently cant get out of its own way with the 305 tbi..

As far as suspension goes, probably just a 2" or 3" ord shackle flip and 33's.. Just a nice stocky look..

And keep in mind, if I do build this 12 bolt, nothing will be stock internally. everything will be beefed up.

I wouldn't mind a one ton axle, it just seems way overkill for my application and I dont really care to have 8 lug axles.

& You're awfully spoiled living in Colorado! Here in Missouri all we have is mud.... Which I hate with a passion. You guys have all the good stuff!

 

[Bent77]

Wow, that is not what I expected to hear. Huh.. And thanks for finding those ads! My ultimate goal for this truck is building it as a cruiser.. I want to be able to hop in it and cruise 500 miles without an issue. Not saying that it wont see mild off road conditions here and there, but nothing extreme. And it should be making roughly 400 or so horse, so it will be fun to beat up on newer trucks occasionally... This truck currently cant get out of its own way with the 305 tbi..

As far as suspension goes, probably just a 2" or 3" ord shackle flip and 33's.. Just a nice stocky look..

And keep in mind, if I do build this 12 bolt, nothing will be stock internally. everything will be beefed up.

I wouldn't mind a one ton axle, it just seems way overkill for my application and I dont really care to have 8 lug axles.

& You're awfully spoiled living in Colorado! Here in Missouri all we have is mud.... Which I hate with a passion. You guys have all the good stuff!

There's a 6 lug 14BSF. I'd go that route before a 12b. It is what I replaced my 12b with

 

[454Sub]

There's some pretty nice rocky off-road parks in MO. Where you at? I live just outside of STL on the east side.

 

[4x4blaze]

There's a 6 lug 14BSF. I'd go that route before a 12b. It is what I replaced my 12b with

Wow, how common are those? I just feel like that's beyond overkill for this mall crawler that I'm building.. And I'm not sure how much a truck and car 12 bolt differ, but my father has a 12 bolt in his Camaro that pushing roughly 700 horse.. and it's held up fine with its brute strength differential and sticky tires..

There's some pretty nice rocky off-road parks in MO. Where you at? I live just outside of STL on the east side.

I live just outside of STL on the west side! And honestly I four wheel my atv, but this blazer is honestly a mall crawler lol.. it's all original sheet metal that's rust free.. Its my baby.. I want it to be able to sh!t and get on the street,(for what it is, I have no desire to go fast in a k5, I just want it to be somewhat quick) but I never really plan on blasting through gnarly trails and rubbing up against trees and whatnot.. It's just a driver and that's what I plan on using her for! What parks do you normally go to?

 

[Bent77]

Wow, how common are those? I just feel like that's beyond overkill for this mall crawler that I'm building.. And I'm not sure how much a truck and car 12 bolt differ, but my father has a 12 bolt in his Camaro that pushing roughly 700 horse.. and it's held up fine with its brute strength differential and sticky tires..




I live just outside of STL on the west side! And honestly I four wheel my atv, but this blazer is honestly a mall crawler lol.. it's all original sheet metal that's rust free.. Its my baby.. I want it to be able to sh!t and get, but I never really plan on blasting through gnarly trails and rubbing up against trees and whatnot.. It's just a driver and that's what I plan on using her for! What parks do you normally go to?

Car and truck 12b are 2 different axles, also under 2 different weight vehicles

And yeah, I've abused 12b in a car. With lots of aftermarket parts

 

[454Sub]

We hit Moonlight in Sullivan, Bricks, Buchanan's, Robertsville, St Joe occasionally, there's quite a few places here locally that we mess around with. I am going to try not to bash mine up but in reality it's to big and to long to do what I'm going to ask, but that's ok. Mines about to be back on the road maybe next month. But back to you. I would look into that sf14 with 6 lugs and be done.

Edit. Find one with 4.10s if you can. Help that 700 last with 33s much better.

 

[4x4blaze]

Well I believe you guys have talked me out of the 12 bolt. And this is why I love CK5! So the truck 12 bolt has a smaller pinion, but larger ring gear, and the 10 bolt has a larger pinion but smaller ring gear. But there is a big difference between car 12 bolt vs. car 10 bolt strength wise..

It really seems like all of you guys want me to go with a 14bsf... I just am not crazy about that big of an axle, but I'm sure it is the best decision... I just hate that the damn thing weighs 550lbs... and a 1 ton axle just seems way overkill for my application... So I guess as of now I'll stick with my corporate 10... Would this axle be worth building to withstand 400+ horse and 33" tires? Or would that just be a waste of money? Are there any other choices of half ton axles out there that I could build to withstand this application? (And just because it will make decent power doesn't mean I'll constantly be thrashing it)

The other reason I was attracted to the 12 bolt (before I knew this) was because it would be a direct fit since it was coming out of another K5.. I do weld, but I don't really want this to be a huge project. But it sort of looks like its going to be either way!

& thanks a lot for sharing your expertise with me guys! That's what makes this forum so great!

 

[4x4blaze]

We hit Moonlight in Sullivan, Bricks, Buchanan's, Robertsville, St Joe occasionally, there's quite a few places here locally that we mess around with. I am going to try not to bash mine up but in reality it's to big and to long to do what I'm going to ask, but that's ok. Mines about to be back on the road maybe next month. But back to you. I would look into that sf14 with 6 lugs and be done.

Edit. Find one with 4.10s if you can. Help that 700 last with 33s much better.

Oh, alright! I've been to every single one of those places and events before! Maybe I'll see you and the suburban there someday, who knows!

And I believe I have 3.73's currently, but I've never had the cover off so I couldn't tell you for sure..

And I'm planning on having my 700 built or purchasing a new built one when I drop this engine in.. but, that's a discussion for another day!

 

[blazer74]

DA, For a 100 bucks in good condition a 12 bolt will be fine if it's the correct ratio, with a gov lock u know what u have.
Simple swap and bleed brakes.

If you need a rear now.

You can then find a 6 lug 14 sf from a 88 +. Get it ready, move the mounts, install with a conversion ujoint, ubolts,springplates etc.
The 6 lug 4x2 version is 65" wide, 4x4 version is 68" wide. A 12 bolt is just under 64" wide
I've beat on my open 12 bolt plenty with 35's( no rock crawly). It is hurt and will be replaced with a 14sf which I already have but not built up. I'd throw another 12 bolt in there for a while for that price.

My problem is time.

My 74k5 is a driver these days also.

IMHO.

 

[Smokinthehippies]

The 14bsf is not that huge of an axle. It's bigger than a 10b, but considerably smaller than a full float with way more ground clearance.
Mine has held up to 4.88s and 39.5" tires thus far.

But if I had 12b sitting in my hands already I would throw that bitch in and see how it goes. A lot of it like anything, is going to depend more on your right foot.

 

[FOR MUD]

For $100 ( If the right gears ) Throw it in there and run it till it goes.... I ran a 12bolt with 38" TSLs for four hard years ( Mud raced, street, farm field beating ) till mine was wore out..... The last year I even welded the gears and welded striped pinon nut in place.
Now if you said you were planning on hitting rocks or hard trails..... Then I would say start looking at tons.

 

[454Sub]

If you find one locally but can't pick it up I can grab it for you and hold it. I can rebuild the 700 for ya cheap too. Simple tranny's.

 

[FOR MUD]

I can grab it for you and hold it.

Must be an Illinois thing to do..........

 

[454Sub]

Bahahahaha.

 

[4x4blaze]

You guys are brutal!

But thanks for all of the replies! I've made up my mind and have decided to wait for a 14 bolt semi floater to show up... I researched the one that @handloader90 shared with me, but unfortunately it's in Peoria Illinois which is quite a cruise for me from STL. So hopefully I'll be able to find one closer shortly. And what trucks did these typically come under? And what are they referred to as? Are they somewhat common?

& thanks a lot @454Sub ! I'll remember that!