(Getting shafted by a) 14bsf build

[4x4blaze]

So, another can of worms! The axle is an AAM 9.5. Same as the chevy 9.5, but slightly modernized with disc brakes, drain plug in the housing, different disk brake mounts and other minor differences. Still uses the same axle shafts, center section, everything. Looks like it's out of a 2008 - 2018 GM.

The issue is, (I do not believe) these were ever offered in a 6 lug variant. Which isn't a major issue since I have 6 lug shafts that will work perfectly, but it does become a major issue when it comes to brakes. I've read that 6 lug versions came in "vortec max" trucks, but can't find any concrete evidence. And even if there was a disc brake 6 lug setup, it more than likely would not work with my 15" wheels which I am bound and determined to keep.

So here is my crazy idea along with my good friends who is a very skilled machinist. Use k1500 front rotors and the calipers off a 87+/- K5 Blazer and machine a custom bracket that will mount it to the factory mounts on this newer axle. If the original brake mounts are too far away/not usable, they will get deleted and a new bracket will get welded to the axle tube.

Lots of figuring/machining/fabricating, but that's all part of it! As far as a parking brake goes, it will probably get a line lock setup like some of you have mentioned.

Various pictures from the tear down

 

[4x4blaze]

& Also, I never posted picture of the truck this axle is being built for.

My 1975 full top K5 Blazer. It's a purists nightmare, but I built it for me. 6 point roll bar/cage tied into the frame with door bars, paint and body done by a good friend of mine, everything else mechanical done by me! Just a fun hot rod 4wd truck I primarily built to cruise around in and have fun!

 

[Blue85]

What gear ratio is in the new 8-lug axle?

In THIS THREAD, Glen says that the 6-lug version was on 6.2L 1/2-ton trucks. The easiest thing would be to find shafts and rotors (or really the whole brake) from one of those, but it's probably hard to come by.

That being said, what you propose is pretty similar to what I did on my 14B s/f. I used front rotors from a GMT400 (these slip on from the outside) and the backing plates and calipers from the front of a squarebody. After the backing plate opening was enlarged and the larger 4-bolt pattern drilled in, I made spacers to line it up, although moving the mounting flange would probably have been better.

I would look at a newer rotor to base this on and try to keep the parking brake. The squarebody rotor is supposed to attach to the back of the hub, which may be difficult to duplicate in the back. I would start looking at anything 6-lug from like 2000+ that came with a drum-in-hat parking brake. That hat diameter is key. You can account for a slightly different overall diameter with adjustments to the backing plate. Also, front calipers are relatively large and may reduce clearance to the wheel. Rear calipers are typically smaller than fronts and this helps with the bias.

Don't forget that you may need a master cylinder swap or a proportioning valve to get the bias right. There are lots of threads on disc brake swaps. Nice looking truck and this axle will be a good upgrade for it.

 

[sweetk30]

www.car-part.com

Find the axle you want and skip reinventing the wheel at this point . Then you get parking brake and any parts store on a sat / sun has parts on the shelf .

 

[4x4blaze]

www.car-part.com

Find the axle you want and skip reinventing the wheel at this point . Then you get parking brake and any parts store on a sat / sun has parts on the shelf .

I really do wish it was that easy. The issue is, is that none of the factory brake setups will work with 15's. All of the conversion kits also state 16" wheels, possibly 15's if steel. And, as previously mentioned by other members, the Eldorado calipers aren't the greatest. So therefore, a line lock parking brake (if I decide to install one) would probably be superior.

& Also, every single part I will be using, besides the brackets, will be available at any parts store.

So no, this isn't the easiest task, but a little fabrication never hurt anyone!

 

[4x4blaze]

What gear ratio is in the new 8-lug axle?

I have 2 sets of 3.73s and a set of 4.10s. Not sure if I will use them yet. One of the sets of 3.73s look like they've got a couple miles on them.

In THIS THREAD, Glen says that the 6-lug version was on 6.2L 1/2-ton trucks. The easiest thing would be to find shafts and rotors (or really the whole brake) from one of those, but it's probably hard to come by.

Good to know! And I already have the shafts, but the problem is, even if i did find one, is that I highly doubt they will fit 15's.. This axle I most recently purchased has some big rotors with dual piston calipers. No way they would fit a 15, and honestly they are way overkill for my 4000lb blazer.

I used front rotors from a GMT400

Those are exactly what I'm planning on using.. k1500 front rotors, and yes, they will probably end up being very similar when finished!

I would look at a newer rotor to base this on and try to keep the parking brake. The squarebody rotor is supposed to attach to the back of the hub, which may be difficult to duplicate in the back. I would start looking at anything 6-lug from like 2000+ that came with a drum-in-hat parking brake. That hat diameter is key. You can account for a slightly different overall diameter with adjustments to the backing plate. Also, front calipers are relatively large and may reduce clearance to the wheel. Rear calipers are typically smaller than fronts and this helps with the bias.

Yeah, It would be nice to maintain a drum in hat parking brake, but I'm pretty doubtful that will happen.. I will probably go with a line lock style if I decide to install one. & Again, the problem is, is that 15s were obsolete by the 2000s.. So, chances of them clearing and working are slim to none.

& Yes, the front calipers are way overkill for rear brakes. BUT. I have a wilwood master cylinder with an adjustable proportioning valve, so I should be able to get it dialed in.. The reason I'm going with the fronts in the back is because of the "slider pin" design and I KNOW FOR A FACT they will fit inside 15" wheels.. So, we will see! There could potentially be a market for these brackets, who knows! They will be on a CAD file.

 

[dyeager535]

Try the 15's with the correct axleshafts and the 14SF calipers.

It COULD be possible they would fit with some grinding.

These are 6 lug rear disk rotor apps (exact years and not range because a lot of things changed. Other years undoubtedly exist, I just did specifics to find some options):
2014 & 2017 Silverado 1500 (13.58" OD, 4.1" height) AC 18A81032
2001 Silverado & 2004 Avalanche (13" OD, 3.76" height) Durago BR55067
2004 Astro Rear (12.795" OD, 3.35" height)

For reference a 1985 K5 front rotor is 11.86" with 2.3" height.

My feeling is that PERHAPS the taller rotors set the caliper inboard far enough that caliper clearance won't be as much of a problem. It looks like your 14SF 8 lug rotors are inboard the same amount (~4") but you'd have to knock the studs out of the axleshaft to see if the 15" wheel is even close to clearing the caliper. I'm sticking with OEM 15", so your results may not be the same as mine in any case. But the OD of the wheel, if nothing else, will be the same.

First time at the wrecking yard for my own stuff in quite awhile this past weekend, but they wanted $80 for one side of a GM rear disk setup. Not worth it to me to pay that money for literal junk parts, just to see if it's possible.

 

[sweetk30]

Add a 1" bolt on wheel spacer and they will clear i bet. Or test fit and grind a little .

Sounds like your going the long way around to the end . Keep it simple .

 

[4x4blaze]

Add a 1" bolt on wheel spacer and they will clear i bet. Or test fit and grind a little .

Sounds like your going the long way around to the end . Keep it simple .

The entire appeal of this axle is that it's capable of being much stronger but it's also wider and will have similar width as the front without spacers. A 10 bolt front WMS - WMS is 67". This 14bsf 4wd is 68"..

I'm fabricating the axle to work for my truck.

When it's done it will work on my truck with the wheels I want to run and all will be well! If I wasn't a tradesmen and didn't know how to fab & weld and didn't have skilled friends who specialize in machining, I would agree with you. But personally, it's a challenge and we enjoy it! Will be exactly what I wanted when it's finished.. We're using off the shelf GM parts, with a fabricated bracket.. That's it!

 

[Wes Harden]

For us the weight is not the only consideration of brake size. Tire diameter is also important. The wider rear axle will increase your turning radius, may or may not be important.

 

[4x4blaze]

For us the weight is not the only consideration of brake size. Tire diameter is also important.

I have a lot of confidence that the single piston calipers will be capable of much more braking power that the drum brakes on my current 10 bolt. And this truck is/has been on 33's.. I really don't plan to change that, but I do understand what you're saying.

The wider rear axle will increase your turning radius, may or may not be important.

I've heard that before and currently do have spacers on my 10 bolt. I personally cannot tell a difference. And even if I could, the posi makes it much more stubborn regardless. These trucks just always look like they have a tweaked frame when you're driving behind them and it drives me up a wall.

It's also strange that more *modern* trucks do not follow this trend. My 05 3/4 ton Ram is the same width front & rear.. & apparently chevy 4x4s were too with the wider 14bsf axles.

 

[Chevy305]

The narrower rear end for turn radius isn't used very much today because it looks weird and CV axles today allow for more steering angle than the straight axle u joints of years ago so it's not as necessary. I do know some Ford Econoline vans have narrower rear ends. I did notice a difference between my 10 bolt and my wider 14bsf for turning though not significant.

I can tell you from experience that a 15" wheel isn't even close to fitting on the 6 lug factory disk brake 14bsf on my '12 1500. The drum versions do work though. The 6 lug 14bsf didn't get disks until '08 then any Vortex Maxx 6.0 or 6.2 truck from '08-'13. Then the '14+ truck use a different version.

Anyway I think your plan for using GMT400 brake parts it good, but how sure are you that 15"s will fit? Wasn't the smallest GMT400 wheel 16"?

 

[4x4blaze]

I can tell you from experience that a 15" wheel isn't even close to fitting on the 6 lug factory disk brake 14bsf on my '12 1500. The drum versions do work though. The 6 lug 14bsf didn't get disks until '08 then any Vortex Maxx 6.0 or 6.2 truck from '08-'13. Then the '14+ truck use a different version.

I was assuming so, but thanks for clarifying, & Also that is some great information for someone who might be dealing with this at a later date. Thank you for posting!

Anyway I think your plan for using GMT400 brake parts it good, but how sure are you that 15"s will fit? Wasn't the smallest GMT400 wheel 16"?

So, the O.D. of an 87 K5 blazer front rotor is 11.86, which as we know, fits inside a 15" wheel obviously.

A 96 K1500 front rotor has an O.D. of 11.6. So surprisingly it's a little smaller. Should hopefully work out well.

I did notice a difference between my 10 bolt and my wider 14bsf for turning though not significant.

My personal solution to getting a slightly tighter steering radius would be to hit the gas and spin the ass end around!

 

[Wes Harden]

The narrower rear end for turn radius isn't used very much today because it looks weird and CV axles today allow for more steering angle than the straight axle u joints of years ago so it's not as necessary.

that why new chevy trucks need 40 acres to make a u turn

 

[imiceman44]

that why new chevy trucks need 40 acres to make a u turn

The cv shafts don't like sharp turns so the steering is limited

 

[Blue85]

Plus they're all double-cabs and there's almost nothing with a short wheelbase anymore.

 

[CT-BLAZER]

Rear Disc Brakes on 15" wheels are near impossible....

Had a new S10 with rear discs & 15' aluminum wheels .... curious as if S10 outer ends could be used?.

Curious, your 14 bolt could be returned...

Your making a custom one off... Go the better path + custom build a 9" rear

 

[Blue85]

Rear Disc Brakes on 15" wheels are near impossible....

I don't know...it seems like what I have in the back would clear 15's. It's the same diameter as square-body fronts, which came with 15" wheels. I'm not sure how the shape of the wheel interacts with the spacing of the caliper, but maybe the outer edge of the caliper could be ground, like people have done on Dana 60 fronts.

what you propose is pretty similar to what I did on my 14B s/f. I used front rotors from a GMT400 (these slip on from the outside) and the backing plates and calipers from the front of a squarebody. After the backing plate opening was enlarged and the larger 4-bolt pattern drilled in, I made spacers to line it up,

So, the O.D. of an 87 K5 blazer front rotor is 11.86, which as we know, fits inside a 15" wheel obviously.

A 96 K1500 front rotor has an O.D. of 11.6. So surprisingly it's a little smaller. Should hopefully work out well.

It's worth mentioning here that my pads don't wear all the way to the outer edge. The GMT400 swept surface is a little narrower, consistent with these diameter numbers.

 

[4x4blaze]

Rear Disc Brakes on 15" wheels are near impossible...

Near impossible, not impossible!

Curious, your 14 bolt could be returned...

Your making a custom one off... Go the better path + custom build a 9" rear

There is absolutely no reason to "return" or give up on this project. I purchased the axle with a brand new uninstalled $900 Yukon posi for hundreds less than what it is worth. It was a great deal and I'm glad I decided to look at marketplace when I did!

The only one off part on this axle will be the brackets for the caliper. Everything else will be over the counter parts.

& Yes, 9" ford's are great axles undeniably. I have a 67 Camaro that will be getting a 9 inch at some point in time, and that's a very deep money hole. So for the strength this 14bsf provides, and the price of everything, this should be a great axle. I could probably build 2 for the price of a well equipped 9".

 

[4x4blaze]

Progress is going well! 3D printed our brackets and did a test fit before sending them out to be machined. Very happy with the fitment. Have a set of ORD brake hoses on the way and will eventually install there line lock/parking brake kit as well.