Eaton HO72 Tech Thread

[06h3]

My notes say that I took 0.130" off each side, I feel like that's not right but then again its what's in the spreadsheet when I was keeping track of this stuff.

Thanks. Now to decide what to do. Your .026 total and gtxracer2 is .060

If I go .060 and it’s too much what happens? It won’t lock?

 

[AlxJ64]

Thanks. Now to decide what to do. Your .026 total and gtxracer2 is .060

If I go .060 and it’s too much what happens? It won’t lock?

Check your decimal places. My cuts were off the inside faces of the gears. They were just bumping into each other preventing the clutch to ride up and clear. Trevin's numbers were inside carrier clearances that effectively did the same thing. Start with his number and then bump it up to mine.

 

[06h3]

Your right, thanks. I guess I’ll just start on the smallest and go up.

I finally found the old post. Gtx said .0425 each side so .095 total

Here he said .060 for each side so .12 total

You did .13 per side so .26 total.

gtxracer2 did you end up having to take out more after that old pirate post?

 

[Tech Tim]

I want to try rear steer also. It would be a big challenge on a full body rig with big tires though.

Even if you limit it to 10 or 15°, it would be a huge benefit on the trail.

Kind of interesting aside, that section view makes it seem like the spindles are rotary friction welded onto the housings. That's kinda neat.

Yes, they are friction welded. I got to tour the Dana Off-Hwy plant in NC many years ago, got to see it in operation. Pretty cool process.

 

[gtxracer2]

Your right, thanks. I guess I’ll just start on the smallest and go up.

I finally found the old post. Gtx said .0425 each side so .095 total

Here he said .060 for each side so .12 total

You did .13 per side so .26 total.

gtxracer2 did you end up having to take out more after that old pirate post?

I’d have to measure the thickness of the washers again to verify but my initial record of 0.048” sounds correct. Remember, this is not an exact measurement. This measurement works for my setup, yours may be different. What you’re trying to do is allow enough space inside the locker for the spring to disengage the locker halves when not under power. To find the correct measurement, you’ll want to do some math. Take the 14 Bolt Detroit you’re planning to use and the 14 Bolt carrier case halves it came out of or a substitute. Measure the height from the inside of the case half where the locker side gear sits to the case half itself. Do this for both sides of the case (both halves). Then measure the Eaton case halves, same measurement. The difference between each measurement from 14 Bolt to Eaton is your machining measurement. You can measure the Eaton 17 spline no-spin side gear heights and other pieces inside the locker and compare them to the 14 Bolt Detroit/Grizzly as a similar comparison and this will help you check your math.

Take pictures and record your measurements and report back. ;)

 

[06h3]

I went to 2 junkyards after work today. Between both of them I found 1 14 bolt. 1!!!!!! It was an oddball van 14 bolt so no luck on axle shafts.

Also had a G80 gov bomb so I couldn’t get an open carrier to get dimensions.

Fuck 14 bolts....I have had an easier time finding Eaton stuff.

I’ll try to go to a few others this weekend

 

[GLTHFJ60]

I believed all 14b axle shafts to be the same. The width differences between the variations were all in the hubs.

 

[06h3]

I believed all 14b axle shafts to be the same. The width differences between the variations were all in the hubs.

There are different length shafts, vans, duallys, SRW all had different length shafts. BillaVista said so.

I personally have found shafts around 31,33,36,39in. I need 31 (which I have) and I need a 37in length which does exist. Just gotta find it. Should be easy but it’s not as easy as I thought

 

[GLTHFJ60]

There are different length shafts, vans, duallys, SRW all had different length shafts. BillaVista said so.

I personally have found shafts around 31,33,36,39in. I need 31 (which I have) and I need a 37in length which does exist. Just gotta find it. Should be easy but it’s not as easy as I thought

Ah, I see now. SRW + C&C axles have the same length shafts. DRW may as well, but van ones are wider. TIL!

 

[YotaAtieToo]

I went to 2 junkyards after work today. Between both of them I found 1 14 bolt. 1!!!!!! It was an oddball van 14 bolt so no luck on axle shafts.

Also had a G80 gov bomb so I couldn’t get an open carrier to get dimensions.

Fuck 14 bolts....I have had an easier time finding Eaton stuff.

I’ll try to go to a few others this weekend

That's the 14b DMANbluesfreak is looking for

Junk yards suck now, unless you have a cool old school one.

You could just get a pair of yukon shafts, I've heard they're about the same strength

 

[06h3]

Found an old school junkyard. Got 2 sets of shafts and a 14b carrier for $100. Not the best deal but also idk what’s what anymore with inflation.

I’ll get to measuring the 14b carrier soon. Working on another rig at the moment

 

[GLTHFJ60]

That seems like an OK price. Late model complete 14b go for about 150-250 around here.

 

[gtxracer2]

Does anyone have an open 5.14 third they want to sell me? I just need one in decent shape, 17 spline no locker. I want to swap back and forth between my locked and unlocked thirds. I'm in Seattle area if that helps but can pay for shipping. Thanks!!

 

[gtxracer2]

Going through my H072 stash…anyone need brand new Ruff Stuff disk brake brackets? Make offer and they’re yours.

 

['92 Vegas YJ]

How's the Grizzly swap working out? Have you started yet? I just broke a stock 17 spline HO72 shaft the other day and I'm thinking about going with the 14B Detroit/Grizzly route. I'm currently running a welded setup with stock shafts.

 

[06h3]

How's the Grizzly swap working out? Have you started yet? I just broke a stock 17 spline HO72 shaft the other day and I'm thinking about going with the 14B Detroit/Grizzly route. I'm currently running a welded setup with stock shafts.

I’ve been dragging on it. I am trying to get my F550 done and should be done in the next week. I’ll get started on the Ho72 after that.

 

['92 Vegas YJ]

Well I just ordered a 14B Grizzly today so I'll be working on one soon myself.

 

[Covecrawler]

Does anyone have an open 5.14 third they want to sell me? I just need one in decent shape, 17 spline no locker. I want to swap back and forth between my locked and unlocked thirds. I'm in Seattle area if that helps but can pay for shipping. Thanks!!

I have one in VA if that helps. Lol

I have a 4.57 and a 5.14 if anyone is in need.

 

[06h3]

Ok guys!! Sorry for the delay, been working on the F550 so much I haven’t given this project any time. I think I may be onto something though!

So, Eaton HO72’s from what I have seen, DO NOT have shims between the inside face of the carrier and the side gear. 14 bolts DO.

The first time I took measurements I used some thin metal laying flat on the carrier to measure, who knows how true that thin stuff was. I took 1/2in plate this time assuming the chances of it being true are much greater.

So I measure the differences between the 14 bolt and eaton and the difference was .031.....guess what thickness those shims are between the 14 bolt carrier and side gear?! .031! Guess what the instructions say when you install a 14 bolt locker in a 14 bolt? Remove those shims.....so it seems like the width inside the carrier is identical when you measure the 14 bolt with those side gear shims in there. So I guess I will have .031 taken out of each side and bench test it.

I hope this isn’t a coincidence.

 

[gtxracer2]

I have one in VA if that helps. Lol

I have a 4.57 and a 5.14 if anyone is in need.

Yes! I'll PM you for a cost to ship to me. Thanks!

Is anyone here in the loop for the ARB mods? Which shop is doing the work and are they open to another? I want to get rid of the clank/bang of the locker and my 4l80e shift kit by going to the ARB after all. Looking to have the total cost quoted to me to outfit an existing 5.14 third with the 30 spline ARB.

 

[AlxJ64]

Is anyone here in the loop for the ARB mods? Which shop is doing the work and are they open to another? I want to get rid of the clank/bang of the locker and my 4l80e shift kit by going to the ARB after all. Looking to have the total cost quoted to me to outfit an existing 5.14 third with the 30 spline ARB.

PM In Route

 

[06h3]

Source RD114 Air Locker Fit for GM 14 Bolt,10.5",FF/4x4 Accessories/ on m.alibaba.com

RD114 Air Locker Fit for GM 14 Bolt,10.5

m.alibaba.com

This may be a good locker to modify and test fit before buying and machining the real deal

 

[06h3]

Got my machined grizzly side gears back yesterday. I’m gonna try and get it installed in the next week or two.

This year has been nuts. I haven’t had a weekend home in almost a month. It’s hurting my wheeling and wrenching time…..

 

[Tech Tim]

Yes! I'll PM you for a cost to ship to me. Thanks!

Is anyone here in the loop for the ARB mods? Which shop is doing the work and are they open to another? I want to get rid of the clank/bang of the locker and my 4l80e shift kit by going to the ARB after all. Looking to have the total cost quoted to me to outfit an existing 5.14 third with the 30 spline ARB.

Where are you located?

 

[06h3]

What’s backlash specs on an HO72?

 

[AlxJ64]

What’s backlash specs on an HO72?

In the past, setting up used Eaton gears I've gone on the wider side so long as the pattern still looks good and the contact points don't "smear" the paint under loaded testing. If I were to give it a value I'd be leaning on the fat side of .008 to 0.013 honestly.

 

[06h3]

In the past, setting up used Eaton gears I've gone on the wider side so long as the pattern still looks good and the contact points don't "smear" the paint under loaded testing. If I were to give it a value I'd be leaning on the fat side of .008 to 0.013 honestly.

Thanks, I am going to call up the shop today that did it 6 years ago. I normally setup my own gears but back in 2016 when I was having the 14 bolt locker issue I was stumped and brought it to hoopers rear end (highly recommend them for you so cal guys) they have setup Eaton’s before. They told me about a drag race guy that kept spitting out rear ends and went to an eaton and they never saw him again….when I pulled mine it was at 20 thousandths backlash! Which seemed way outta way. Pinion bearing preload seemed perfect. It’s still using the original barrel style bearings.

With that said, I see replacement carrier bearings online. They are tapered roller though. Can you switch the carrier bearings out to tapered roller bearings or no?

 

[AlxJ64]

Thanks, I am going to call up the shop today that did it 6 years ago. I normally setup my own gears but back in 2016 when I was having the 14 bolt locker issue I was stumped and brought it to hoopers rear end (highly recommend them for you so cal guys) they have setup Eaton’s before. They told me about a drag race guy that kept spitting out rear ends and went to an eaton and they never saw him again….when I pulled mine it was at 20 thousandths backlash! Which seemed way outta way. Pinion bearing preload seemed perfect. It’s still using the original barrel style bearings.

With that said, I see replacement carrier bearings online. They are tapered roller though. Can you switch the carrier bearings out to tapered roller bearings or no?

Yea, there is a lot of room for play in those axles. The bigger the tooth and the bigger the ring the more backlash that can occur based on shape and contact areas.

As for the bearings... You can, but the spehericals are just so much more forgiving on loads and misalignments. They operate in an orbit so if something is deflecting in the housing under load, they can transmit contact into another portion of the race vs high loading a section of a "squared" shape bearing.

The taper bearings 382 cup and 388A cone do fit and will work... but they suck compared to originals IMO.

I actually have some older NOS BCA brand 388A cones for sale on eBay right now. NOS as in like early '80s production.

 

[06h3]

I called up hoopers and asked him what he thought. He said they usually setup HO72s at .010-.015. I was at .020 but he said make sure the pinion isn’t moving when you rock it back and forth. Normally on new diffs the pinion is tight enough to not have any pinion movement and you can just rock the ring gear back and forth. On these older HO72s he said you may be picking up another .005 if your not holding the pinion down tight. Admittedly, I didn’t do that and it’s apart now. So who knows….I’ll set it back up to .011ish while holding the pinion.

How does one “bench test” a Detroit locker? I wanna bench test mine before slapping it all back together.

Here are some pics of my bearings/races.

First pic is the worst. You can feel the ridges in the roller. That’s the only roller like that between both bearings.

2nd pic is light pitting. Maybe 3-4 are light that between both bearings.

3rd pic is some small imperfections in the race.

This diff didn’t make noise when it was pulled. It’s been in for 6 years and about 30k miles. It’s been up to 90 mph. It has spent many 8-12 hour days at 70-80 mph in 100+ degree heat.

It’s been under a 7k lb rig on 40-43s dragging dead U4 cars, heavy rigs, light rigs, etc. the diff has seen some abuse.

The only reason it was pulled was to test 14 bolt shafts/locker and it’s the first time I pulled the 3rd since install in 2016.

So, run it? Find new tapered roller bearings from orielly? Or try and pull a better condition bearing off another one of my HO72s and put it on this one?

 

[gozuki]

If it wasn't noisy or hot, I'd run it.