72 K20 Rear Axle Swap

[ssuth9]

Hello, I have a 72 K20 with an Eaton H052 in it.. I'm looking to upgrade/install a 14 Bolt with Disk Brakes..

Does anyone know what year truck would fit my K20?
I do have a 14 Bolt 10.5 FF out of a 2004, but it's a bit long. It would need to be shortened..

Or does anyone know the cost to shorten a rear axle?

Thanks for the help..

[franken]

As I recall, the 14 bolt FF came out in 75 and that cab and chassis versions had the same spring center to center as 67-72. Not sure on the WMS width though. The squares also have different shock mounts so nothing is going to bolt in directly.
You can convert your rear (or a 14b w/ drums) to disk using 3/4 ton front rotors and brackets from pirate, but some don't like the Edlorado calipers and their E-brake system. If you don't need that, the 3/4 ton front calipers work.
If it was me, I think I'd look to adapt the 14 bolt disks to the Eaton. They should have a drum E-brake setup in the rotor.

[ssuth9]

Hi Franken, Thanks for the reply.. My Eaton seems to have had an issue in the past (I think)..

Not sure if the pic shows it but the case on both side of the weld are Not at the same level.. And there is a Weld in the same spot on the bottom, both are right in the middle Top and Bottom..

I've seen pics of other Eaton's with welds in the same spot.

[franken]

Does that interfere w/ the operation of the diff?
BTW, a DRW 14 bolt should be the same as an SRW, but uses different hubs. Swap the hubs and you're good to go.
I was on pirate a minute ago: https://lugnut4x4.com/product/62-72-...onversion-kit/ There are a number of people making the brackets and kits.
Just noticed your location--I used to drive up there to work on stuff when I lived in the LA area. Loved that town.

[b454rat]

Need to find one from a 1 ton. Either 2 or 4wd will work. They have the same spring perch width as your truck, just need to redo shock mounts. Discs are easy to do on them, get a bracket, there is a bunch out there, 3/4 ton rotors, calipers and pads, think even brake lines too. On a side note, how much wider is the 14 bolt with discs? Every GM 4wd has the front being wider than the rear, so maybe why it seems so much wider than the stock Eaton. IMO it looks better, track width being the same front to rear.....

[ssuth9]

Originally Posted by franken

Does that interfere w/ the operation of the diff?

Not sure if there is anything wrong with it, hasn't been run by me yet. But Do want to upgrade to Disks in the rear.

Originally Posted by b454rat

Every GM 4wd has the front being wider than the rear, so maybe why it seems so much wider than the stock Eaton. IMO it looks better, track width being the same front to rear

Great point, I have noticed that as well..

My Eaton H052 measures 65" from the Mounting surface (were the wheel mounts)

The 14 Bolt measures 68-1/4" only 3-1/4" wider or 1-5/8" each side.. (Not that much Sweet)

Does anyone know the width on a Dana 44 from each wheel mounting surface on the Rotor? As mine is tore down for rebuild.

[b454rat]

they are aboot 69" wide, give or take...

[ssuth9]

Originally Posted by b454rat

they are aboot 69" wide, give or take...

Well that's Awesome.. Sounds like I just need to relocate the Perches and Shock mounts..
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['63GENIII]

I found a 14BFF from a 2005 3500hd. It came with 4:10s which matched the front, disc brakes and most importantly parking brakes which work awesome. I did cut the perches off and install new ones to match the spring width and change the lower shock mounts to match the existing ones. The best part... the rear axle is only 1" wider (1/2" each side) than the '73 Dana 44 thats in front. I freaked out when I got it home and compared it to the Dana 60 it was replacing. It was nearly 5" wider! It wasn't until I measured the 44 that I realized that the track width would be more in line with the new 14 bolt.

One more note on the 14 bolt. Somewhere along the line, GM started using the AAM axle which has a bigger ring gear (11.5?) and is identified by the lack of a removable pinion carrier. Apparently these are harder to get parts for than the earlier (10.5?) ring gear size. Mine has the AAM stamp, 10.5 ring and the removable pinion carrier though.

TBH, the rear disc brakes are nice but nowhere necessary IMO. The giant set of drums that the 14 bolts come with do a great job for many years if done correctly. The calipers do look cool though!

[ssuth9]

Thanks '63GENIII for the input..

I was happy as well to here the width of Dana 44, cuz I was freaking out a bit myself..

I did find this info on AAM Axles..
Link to 10.5: http://www.demandaam.com/resources/p...0608153906.pdf

Link to their GM line: http://www.demandaam.com/resources/p...0701132709.pdf

Link to various catalogs: http://www.demandaam.com/technical-s...uct-catalogs-1

[Orange Crate]

14 BFF dimensions and everything else here:

http://www.pirate4x4.com/tech/billav...ble/index.html

I've got one in my 72 with discs. Had to move the spring perches and that was about it. Got my disc conversion brackets at Ruff Stuff, good quality and beefy.