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Rear axle swap/upgrade - 6 lug

muddybuddy

muddybuddy

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Wanting to start mapping out plans for the blazer. It is going to be street driven, maybe some beach use (only after underside is treated), max tire will be 33’s or 35’s. Eventual plans are for 400-450hp/tq. Not necessarily planning on towing, but dont want to tip-toe around it if down the line I end up towing. I’m wanting bullet-proof, never want to worry about it, but also knowing things snowball. Have stock rally’s currently and while I do plan to move up to 17’s, was planning to keep it 6 lug so I could put the rally’s back on if down the road I feel nostalgic. 14bff isnt an option (though it has a special place in my heart, just not on this truck)

Would like to have disc brakes (likely would have parking brake on t-case, if not functional/effective on axle).

Options I’ve considered:
-square 10b with upgraded shafts - just cant get on board with investing in a 10b (seems a waste of good money, and not future mod proof) mentally eliminated
-square 12 bolt - though minimal upgrade vs stock 10b so have pretty much thrown it out
-14SF (limited aftermarket support)
-Ford 9” (aftermarket support is strong, could pick and chose what strength level, and parts)
-Newer 6 lug AAM axle:
-9.5” or 9.76” 12 bolt, from 2014+ Tahoe/ suburban
-GMT900 9.5” 14 bolt

Any other options I’m missing/should be considering?

There is a budget, though I dont yet know what it is. This is for a forever truck, so at this point looking for the optimal rear axle then will figure out how to pay for it (or settle for the next best option).

Anybody have experience or strong opinions on the newer axles? Those would likely be drop in (minus spring and shock mounts), vs older axles would need to rebuild, upgrade brakes, shafts, etc.

What do you think? What would you do?
 
I'd look into the newer 9.5" axles. Some of those units came in the H3 with an eLocker.
Anything 10 or 12 bolt is less durable
 
14bsf 9.5 6lug is your best bet. Find a complete one out of a 90's GMT400 truck either high GVRW 1500 or low GVRW 2500. 4wd trucks will be wider but will match your current front 10b.
Anything 9.5 from '99 to '13 are rarer and are usually expensive. Anything '14+ is going to more expensive because it's newer.
 
I put a SF14 in my 70. Think it was out of an 88, maybe an 89. Motor makes 520lbft/544hp with an Nv4500 behind it. Will be street driven and sand dunes.

Made my own disc brake kit with some weld on brackets from Speedway Motors that use a front GM metric caliper and a front rotor from an 88+ light duty 4wd.

If anything ever goes out on it and it's not a cheap fix....it's getting a 9". Those are the SBC of the axle world, cheap and parts grow on trees for them.


Edit: Thought I had a picture of it in the wheel. I'm running a 17" wheels to clear my front brakes (Hummer H3 calipers/rotors). I believe a 16" would clear these though.

20170805_213933.jpg
 
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Appreciate the replies thus far. In my head, I was leaning more towards a 9” for the fact that it can be made extremely strong and the aftermarket support is extensive. I’m sure the 14sf is the cheapest route to get in the truck, so there is appeal there. The newer axles have nice disc and parking brake setup from the start, so I’d be ok paying more for a complete setup vs having to do disc conversion, so that cost is something I’m tracking of course.

One of the must haves was equal track width as the front; i’d prefer not to run spacers to make them equal.
 
In the late 2000s chevy gmc express vans is a 6 lug semi float disc dana 60. I have forgotten the specifics of it but it does exist.
There are pictures from many years ago in the PAD thread.

As for any of the newer axles they will need a pinion yoke swap or just 1410 driveshaft work. Pretty easy swap relatively.

The newer 30 spline ten bolts are putting down heavy power at the strip and taking it pretty well. I wouldn't hesitate to run a new disc 10 bolt except for my ego just can't handle that.
 
My son was checking into whether or not a '01 and up SUV rear disc would bolt onto a SF14B. We haven't actually tried it because I only have one SF14, but the dimensions are close upon initial investigation.
@obijuank5 is correct that the new 10B has been proven to hold some big power with a carrier change and a girdle cover.

We swapped the SUV brakes onto the kids '01 2wd rear axle. It gave him dual pistons with vented rotors. Got the swap parts for free when we scrapped an Escalade.
 
muddybuddy said:
Appreciate the replies thus far. In my head, I was leaning more towards a 9” for the fact that it can be made extremely strong and the aftermarket support is extensive. I’m sure the 14sf is the cheapest route to get in the truck, so there is appeal there. The newer axles have nice disc and parking brake setup from the start, so I’d be ok paying more for a complete setup vs having to do disc conversion, so that cost is something I’m tracking of course.

One of the must haves was equal track width as the front; i’d prefer not to run spacers to make them equal.
Click to expand...
I've looked into swapping '99+ 10bolt disc setup onto the older 9.5 14bsf and you basically need either a spacer for the backing plate flange or to weld on a new flange at the correct depth. This link sells the spacers. They aren't cheap so the weld on flanges from Ruff Stuff might be a better alternative.

https://1320wheels-com.3dcartstores...S-10-Bolt-Brake-Conversion-Spacers_p_105.html


From there you can buy the backing plates and everything new from Rock Auto except this one aluminum bracket that hold all the parking brake stuff. That you have to source used from a junkyard or something.
 
Quick Performance 9" hands down.
Ive got one from them and a 10" (9.5 actually after machining) from Currie and would never go back.
Especially not to a big heavy SF 14 bolt.
35 spline axles and a Truetrac is super tough and reliable. I beat on mine and havent ever had an issue.
Quick Performance has better prices than Currie and you can pick about all the same options.
 
For 33’s I would stick with the 10 bolt. Add carrier of your choice and 30 spline shafts. I went with Dana “SVL” I think ring and pinion, auburn limited slip, timken bearing set and dana 30 spline shafts for about $600 on the last one I did. I’m not scared of it breaking and if it does I can do it twice more for the price of a late model 14 bolt with discs from the junk yard…

If you can find a set of axles from a LD 3/4 ton they’re usually 4.10. A 9.5 SF/Gov Lock and a 10 bolt with a lunchbox locker in front is a bad ass combination for a small tire rig although it’s 8 lug.

I run that setup with 17x9’s and 33x12.50R17’s on my Suburban. 2” Tuff Country HD’s (6.2 Diesel) and a custom 7 leaf stack out back. Perfect for what I do with it…

A custom 9” is definitely the high dollar answer but if you want to spend $$$ it will do what you want. I’ve grenaded more 9” Fords with 33’s than 10 bolts though…
 
Big fan of the new ‘14+ 9.5” 12 bolts. Basically an upgraded 14SF with factory discs.
 
Best I can tell for the 14SF, 15" ralleys are the problem with discs designed for that axle. They most certainly won't clear the rim.

I haven't spent a ton of time looking at physical parts, but if there were rotors with a real deep offset, perhaps they could be inboard far enough (plus a bit of caliper grinding if necessary) to clear.

Later 10 bolt disks could be an option too? This is why it would be nice for someone to turn out a 16" ralley clone. Not sure if all 14sf disks were the same, but the vans were running 13" rotors...
 
AJMBLAZER said:
Big fan of the new ‘14+ 9.5” 12 bolts. Basically an upgraded 14SF with factory discs.
Click to expand...
Yeah, I missed the part about using the factory rally's possibly. The 14+ 9.5" and 9.76" 12 bolts need 17" and bigger rims to clear the brakes.
 
Are there any rotors designed with really deep offsets for the rear disk/e-brake setups? I really need to see the components of that setup to see what kind of adapting can be done. I too prefer the ralleys, I have yet to find an easy and relatively inexpensive way to get disks on the 14SF that will clear them.

Obviously there are options like driveline brake, Cadillac calipers, and front calipers on the rear, but the later disk e-brake setup IMO is a very good design, and if it can be made to fit with a minimum of effort, would be much preferred to the alternatives.
 
AJMBLAZER said:
Big fan of the new ‘14+ 9.5” 12 bolts. Basically an upgraded 14SF with factory discs.
Click to expand...
Do any parts swap between the GM 9.5" (14B s/f) and the '14+ 9.5" (which I assume is AAM)? You know, axle shafts, gears, lockers, etc. I know there are some parts you can use from the RAM 9.6" front diff and I believe that's all AAM.
 
The newer 6 lug rears are nice and beefy but as far as I know there isn't a lot of aftermarket support for them yet. My '22 Sierra 1500 with the babymax has the 10 speed auto and only 3.23 gears which would suck with the tranny's we usually have in our squares. I think some of the 2014ish trucks with the max trailering package might have 3.73's that could work well with 33's.

For what it's worth the rear disc brake setup from the GMT800 trucks/SUV's will work on the 6 lug 14BSF with a spacer or new backing plate like someone mentioned above and there's a lot of swap info over here:

Official 14 Bolt 9.5 SF Truck Thread - PerformanceTrucks.net Forums

GM Drivetrain & Suspension - Official 14 Bolt 9.5 SF Truck Thread - First Lets start off with some Links on different types of 14 Bolt 9.5 SF Builds and swaps... Custom build and swap EVILGMC 14 BOLT BUILD (mucho pictures) - PerformanceTrucks.net Forums...
www.performancetrucks.net

I was going to go that route before I found my Dana 60 and went with a newer 14BFF instead but I still have the Ruff Stuff brackets if you want them.
 
Honestly without some kind of major compromise or expense I don't see how you run modern disks with a 15" wheel. Really your best bet is to get a gmt400 axle and just be happy with the drums. They are bigger that the 10b drums and have a good parking brake setup.
 
NorCalAnthony said:
The newer 6 lug rears are nice and beefy but as far as I know there isn't a lot of aftermarket support for them yet. My '22 Sierra 1500 with the babymax has the 10 speed auto and only 3.23 gears which would suck with the tranny's we usually have in our squares.
Click to expand...
This is a good point. New trucks have 10-speed transmissions with super low first and double overdrive, so they tend to have weeny differential gears compared to what we run in old trucks, so gear swap or doubler expected.
 
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