14 bolt SF axle build

A

a-fuso

GMC Owner
Mar 28, 2012
1,856
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CA
Well tried a local truck pull last Saturday, and I'll let the video explain what happened...


Well that ended in this.


We towed it home in style on a good friend's lowboy


So that brings us to yesterday, when I finally pulled the rearend apart



Good news is it's time for an upgrade, so I got a 9.5" 14 bolt from a obs 2500 6 lug and am going to have to move the spring perches, shocks tabs, and caliper mounts to use my disc brakes and have shocks both on the rear of the axle.
Also doing a full rebuild of the axle, all new bearings and seals, and installing a Detroit locker.

 
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Ginger said:
power coating anything while doing this?
Click to expand...

Nope no powder, this truck sees the dirt way too much for a powdered axle, waste of money imo. I'm just gonna shoot it with gloss black when I finish.

Update: I got all the parts in today from summit with the exception of the axle bearings and seals. I have cut off and relocated the spring perches already, and stripped the drum brakes off. Also got the shock mount moved over to the rear. More progress on saturday
 


Yesterday's pic, but as of this evening I have the whole axle wire wheeled bare. I also cut the brake flanges off the 10 bolt and am having a buddy machine them open larger tomorrow morning to fit over the 14 bolt axle tubes. This way I can remove the drum brake mounts and install the new mounts for the disc brakes in the correct location further out and on a 45* angle. Should be ready for primer tomorrow afternoon.
 
Started yesterday morning by milling the stock 10 bolt brake flanges, smoothed off the backsides to get a true parallel, then bored out the center diameter bigger to fit over the 14 bolt tubes.



Used the original pieces to get the new ones on straight, then checked by assembling all the brakes.



We also machined .050 off the axle flanges outer diameter to make sure it fit inside the stock rotors.



Then I moved the axle back to my shop and cut off the old flanges with a cut off wheel and grinder, and cleaned up with a flap disc.



And the final shot is the entire axle, all cleaned up in bare metal, ready for the two brake line brackets, then a final wash and painting


 
Got it all prepped yesterday. Self etching primer, then Industrial enamel gloss black




Then today, I bolted on the backing plates, which I also sprayed, and pulled out the old axle bearings. They put up quite a resistance, but I was able to pull them loose



I also cleaned up the rear calipers with NAPA brand aluminum bright, this stuff works great for bringing a like new shine back to cast aluminum

 
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Got everything buttoned up today. Had my dad and uncle help me setup the gears after changing the carrier and all new bearings. Everything went in smoothly, and seting backlash was the only major issue. I used the factory pinion shim to leave depth unchanged. But had to remove the factory shim on the carrier and replace with ones a few thousands less to get backlash within spec. We now have a backlash of 0.007" within the specs of 6-10 thou.

The gears were really easy to setup and adjust too because this axle uses an threaded adjuster on one side, like the full floater axles have. No messing with setup bearings.

The axle now has all new bearings and seals in it.




I put on the brakes, had my rotors turned, and new pads. Then mocked up the 10 bolt brake lines. They hit the diff cover and housing, but with a little bending I got them to work with the bigger housing, and used the stock 10 bolt bracket on top of the diff





You can see it here, sorry the pics came out blurry. I also modified the bracket that hold the brake t to have the rubber hose come out vertically now so I won't need to get a longer hose when I droop out my rear axle now.

I also have a chrome diff cover I will put on after I do a break in period.
 


Axle is done and in so I can drive my truck finally. Still need a few other odds and ends yet though.
 
Awesome work! But I ask why you went so far as to do that much work and not upgrade the rear brakes in the process? Its a simple swap to switch from your stock single piston calipers to the dual piston calipers that came on the NBS Suburbans and Yukon XLs. Just need the calipers, pads and the bigger rotors. Maybe you can do that in the future when its time for a brake job.
 
I thought about it scotty, but it was going to cost more than this whole mistake already did. Plus my truck stops better now that I don't have 120xxx mile rotors and pads on the rear axle anymore
 
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