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Eaton HO72 Tech Thread

Thank you AlxJ64 for your insight. It does make me feel better knowing that it seems like the failure was due to cause and effect on hurt parts vs me exceeding the physical strength of the Eaton Ring and pinion. I had a hurt carrier bearing allowing odd pattern wear. It further proves the point that I had another carrier in the axle with new carrier bearings when I installed it in 2016. When I switched the 14 bolt locker setup, I didn’t reuse that carrier. It was easier to setup a new locker with an existing carrier I had laying around then to pull it all apart and wait for the machining on locker/carrier parts, the carrier I put in had those old carrier bearings.

I have more 5.14 gear seats. I’ll work on getting a new one swapped in.
 
This solidifies the failure point to a carrier bearing in my opinion.

I haven’t seen what load bolts look like on race cars but in my mind a load bolt should wear evenly as the ring gear presses against it during deflection.

The pics are tough to see but in person it’s easier to capture. The groove on the top part of the load bolt, that’s not a single groove, everything to the top of that “line” is worn higher than everything below the “line.”

The other pic doesn’t really do it justice but imagine an ever so slight angle worn the entire way up to the groove.

So that carrier bearing was allowing the ring gear to deflect not just away from the pinion tooth in a normal deflection pattern but also in a side loading pattern.

Unless uneven load bolt wear is normal:confused:
IMG_9047.jpeg

IMG_9046.jpeg
 
06h3 said:
This solidifies the failure point to a carrier bearing in my opinion.

I haven’t seen what load bolts look like on race cars but in my mind a load bolt should wear evenly as the ring gear presses against it during deflection.

The pics are tough to see but in person it’s easier to capture. The groove on the top part of the load bolt, that’s not a single groove, everything to the top of that “line” is worn higher than everything below the “line.”

The other pic doesn’t really do it justice but imagine an ever so slight angle worn the entire way up to the groove.

So that carrier bearing was allowing the ring gear to deflect not just away from the pinion tooth in a normal deflection pattern but also in a side loading pattern.

Unless uneven load bolt wear is normal:confused:
Click to expand...

Agreed, and it makes sense too with the pics of the load bolt. The ring side bearing was worn and allowing the carrier to pitch. The side gears were holding things lined up and using the moment of the axle shafts to keep things somewhat in place, and the Load Bolt would step in some too it appears. Yea, that carrier was bouncing around in there and the pinion finally ran off the ends of the teeth under some hard loads and snap crackle pop.

Build the next one and keep on runnin!
 
Building the next one now, pattern has been tough to get. I’ve never had to mess with pinion depth on an HO72. They seem to just line up. This one may be different

IMG_9089.jpeg

IMG_9093.jpeg
 
AlxJ64 have you set up gears on an HO72 before? It looks like I should be adding pinion shim to pull the pinon away from the ring gear right?

The drive pattern looks ok (may needs to go a hair deeper into the root) but the coast is wonky.
 
Thanks, I’m a bit too far for that. I found one 300 miles from me. Just gotta get up there to get it
 
06h3 said:
-14 bolt axle shafts and the drop in (detroit, grizzly) locker fits in the HO72. There are some exceptions, on some older open carriers they are a tad narrower and do not let the 14 bolt locker unlock. Some have fixed this with washers between the carrier or machining a few thousandths off the side gear. I machined .008 off each side gear for a total of .016 and it now locks/unlocks like it should.
-

Could you tell me if these are the two faces you took .008 to get a locker in your ho52? Or is only one face needed to be machined?
801D6F39-3253-4826-AFC2-7C1D3B2F9551.jpeg
Click to expand...
 
I’m circling back on the set of axles I built years ago with hopes to actually get them in the jeep soonish. The front housing is with 05+ outers. Both with rough stuff covers. The rear has 14 bolt brakes with custom brackets. 5.14 in both with 14 bolt locker in the front and factory locker in the rear. The plan is branik 1550 shafts in the front.
I was looking into going 6x6.5 bolt pattern (cheap used beadlocks) but I’m not sure if I could re-drill the 4 needed holes in the rear hubs with how they are designed.
 

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I know a friend drilled 14 bolt hubs to 6x6.5 pattern. He just used a mill to recess the head for the wheel stud to go closer to the WMS so he could run studs he had. he milled them so the 1" or whatever knurl length 5/8" studs he had would work for all 6 studs. The factory studs on that hub had a thicker spot where the studs went so he had to machine that down so the wheel stud head would have a flat spot to press against.
 
TTMotorsports said:
I know a friend drilled 14 bolt hubs to 6x6.5 pattern. He just used a mill to recess the head for the wheel stud to go closer to the WMS so he could run studs he had. he milled them so the 1" or whatever knurl length 5/8" studs he had would work for all 6 studs. The factory studs on that hub had a thicker spot where the studs went so he had to machine that down so the wheel stud head would have a flat spot to press against.
Click to expand...
It looks like the Eaton hubs are the same as the 14 bolt hubs with the inconsistent thickness. That’s what I was concerned with.
 
Yeah will have to be a 2 step re-drill. Use template to drill from the top with the mill. Then clip over and end mill the back side flat for wheel stud to press against. Not impossible but more work, to save on wheels.
 
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They can probably build you some. Just make sure they are hub centric since 2 piece is kinda sketchy and that will be less sketchy I'd think. Doing a 2 piece adapter isn't common and may have to find a machine shop to draw/machine them for you. Probably easier to machine your hubs and not worry about an adapter.
 
WRAMBLERGUY said:
Who makes those? I couldn’t find any
Click to expand...

Also those look like 6x5.5 chevy adapters since lugs are close to the centerbore of the wheel/hub. Probabaly done to get a full floater/wider rear axle on a prerunner. I welded/machined the 14 bolt hubs to 6x5.5 to put that on my brother 01 silverado prerunner. Machined axles down to 4.25" machined the flange on the 12point axle bolts down so wheels would slide on/off without problem.
 
TTMotorsports said:
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They can probably build you some. Just make sure they are hub centric since 2 piece is kinda sketchy and that will be less sketchy I'd think. Doing a 2 piece adapter isn't common and may have to find a machine shop to draw/machine them for you. Probably easier to machine your hubs and not worry about an adapter.
Click to expand...
Iirc I built the front 4” wider than the rear planning on running 2” adapter to 8x170. So I would really need some kind of spacer even if I reworked the brakes and put the wider hubs on it.
Can you tell I can’t make up my mind
 
WRAMBLERGUY said:
Iirc I built the front 4” wider than the rear planning on running 2” adapter to 8x170. So I would really need some kind of spacer even if I reworked the brakes and put the wider hubs on it.
Can you tell I can’t make up my mind
Click to expand...

I wouldn't worry to much about the width difference, lots of guys run staggard wms like that.

A 72" 05+ D60 and 67" rear 14b is a super common combo. Fwiw
 
Hello fellas,
I am looking for a ring and pinion in 4:10 for a HO52/72 if anyone has one. Sadly, my restored 1972 C20 is currently living as a lawn ornament due to damage on the original pinion shaft.

It might be a long-shot, but I know most of your rigs use lower gearing, and thought someone might have pulled a 4:10.

Thanks in advance!

-Chuck.
20241115_120729.jpg
 
awryexperiment said:
Hello fellas,
I am looking for a ring and pinion in 4:10 for a HO52/72 if anyone has one. Sadly, my restored 1972 C20 is currently living as a lawn ornament due to damage on the original pinion shaft.

It might be a long-shot, but I know most of your rigs use lower gearing, and thought someone might have pulled a 4:10.

Thanks in advance!

-Chuck.
20241115_120729.jpg
Click to expand...

What does it currently have?

Edit: nevermind, missed the damaged gears. Thought he just wanted taller gears.
 
Last edited:
awryexperiment said:
Hello fellas,
I am looking for a ring and pinion in 4:10 for a HO52/72 if anyone has one. Sadly, my restored 1972 C20 is currently living as a lawn ornament due to damage on the original pinion shaft.

It might be a long-shot, but I know most of your rigs use lower gearing, and thought someone might have pulled a 4:10.

Thanks in advance!

-Chuck.
20241115_120729.jpg
Click to expand...
I'm thinking you might be the guy I referred to this site from that 67-72 board? If so welcome aboard and good luck. Show the pics of your pinion shaft wear and maybe someone can help.
 
awryexperiment said:
Hello fellas,
I am looking for a ring and pinion in 4:10 for a HO52/72 if anyone has one. Sadly, my restored 1972 C20 is currently living as a lawn ornament due to damage on the original pinion shaft.

It might be a long-shot, but I know most of your rigs use lower gearing, and thought someone might have pulled a 4:10.

Thanks in advance!

-Chuck.
Click to expand...

No help, but have you considered using a 14bolt and shelving the Eaton.

Get ya back to enjoying and driving while you tinker the old axle together
 
Gravy said:
No help, but have you considered using a 14bolt and shelving the Eaton.

Get ya back to enjoying and driving while you tinker the old axle together
Click to expand...
That is what I advised him against for the sake of preserving an old truck and keeping an Eaton in use. His pinion gear is worn below the bearing and if he shows a pic of it I figure someone might be able to give better advice than I did for saving the axle.
 
Thanks for your replies. Here's a photo of the damage. My first choice would be to find a new/used replacement in 4:10.

20251126_105423.jpg
 
Deleted my other post, I thought is used the pilot as the inner race like a Ford 9 in which case you could've turned it and run another bearing.

The pinion pilot uses its own inner race. Green loctite and full send.

Screenshot 2025-11-29 at 8.54.09 AM.png
 
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