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Old 07-29-2012, 09:06 PM   #1
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Eaton HO72/HO52 vs. 14 Bolt FF

This thread is dedicated to answering all the questions about the Eaton axles and comparing it to the more readily available Corporate 14 bolt.

Please post questions you have and I will do my best to answer them in this thread.

Please post any errors you see with this info and I will correct it.
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Old 07-29-2012, 09:24 PM   #2
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Interchangeability... Sop far, only the brakes are interchangeable between the 14 bolt and the Eaton. I have seen a lot of requests for part numbers and how-to's for the Eaton brakes. Well, here is my how-to rebuild the brakes on the HO72 and HO52. NOTE: for the 71 and 72 HO72/52 axles this is a direct swap. 70 and earlier use smaller wheel studs and will require a hub swap, or the holes on the hub to be enlarged.

Eaton left 14 bolt right


13 inch 14 bolt backing plate assembled and bolted to HO72. Perfect fit.


This is the one issue with this swap if you are performing it on a 70 or earlier axle. from left to right early Eaton stud, 71-72 Eaton stud, 14 bolt stud.


I went ahead and installed the 13 inch drum on a 69 hub with the small studs for this demo. you will notice the that flanges of the larger drums are also thicker. The studs stick out just 13/16". The drum center fits perfectly over the hub. I would not recommend running the brakes this way without using a spacer between the studs and drum, or enlarging the hub to use the larger studs.


Bam!

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Old 07-29-2012, 09:55 PM   #3
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

I'm all over this like stink!
Thanks for this, since I have 13" drum brakes off a 14FF.
Getting out of the not so common 12" system is going to be a relief.

I want to keep my original diameter wheel studs, so I'm gonna have to search for longer ones to work in this application.

Now, what to do with a 14FF axle with out it's brake system...
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Old 07-29-2012, 11:25 PM   #4
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Chris,

Here is what I was talking about for the studs being smaller...
The I.D. of the holes on the 14 bolt brakes are roughly .552" and the I.D. on the early Eaton is .490" So you are looking at roughly a .030 gap around the studs. Those measurements aren't perfect because of the knurls.

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Old 07-29-2012, 11:47 PM   #5
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Ahh, I see what you mean.
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Old 07-30-2012, 05:34 PM   #6
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Chris,

I am thinking now that running the drums with new stock studs will be OK. Every one of the slide on disc brakes I have done today has a much larger hole than the studs they slide over! As for the length, you are running steel wheels, right? You should have plenty of stud if you have steel wheels.
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Old 07-31-2012, 06:21 PM   #7
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

More Side-by-sides.



Check out the different welds on the 71(top) and 69(bottom) Eaton brackets!





14 bolt and Eaton threads are the same. This is the 14 bolt spindle nut on the Eaton


The 14 bolt bearings are smaller than the Eaton. They have a smaller ID and OD
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Old 11-17-2012, 11:40 AM   #8
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

I want to buy an OEM locker unit for the 52 under my 71 C20. Does the locker unit determine the ratio?
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Old 11-17-2012, 01:03 PM   #9
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Nope! The locker goes inside the diff case halves. You will only find them used, or you can buy buy a detroit locker for a 14 bolt and use 14 bolt axle shafts. You will only need to turn about a 1/4 inch off the splines of the 14 bolt shafts. I have one done this way.
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Old 02-26-2013, 03:37 PM   #10
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Jeremy, first thanks for posting and accepting questions on this subject.

I have recently converted the front drum to disc on my 1970 C20. I would like to stop better and have the same size studs on the rear as well as install a locker. I take it from reading that I have an EATON FF rear. What would I need to change to go to 13" brakes and bigger stud hubs and have my brakes work? Would it be better to get a disk kit from someone like BlackBird and go to disc? Or should I look for a newer rear end with brakes, locker and all in it?

Thanks in advance,

Vince
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Old 02-26-2013, 06:36 PM   #11
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Vince, I'm glad you asked these questions!

There are a few things that you need to know about your truck first. Does it have the Eaton axle or the Dana axle? And, does it have leaf spring rear suspension or coil spring with trailing arm rear suspension?

the Eaton and dana axles are easy to differentiate. the Eaton will have a round diff cover, along with a removeable 3rd member. There will also be 5 bolts around the yoke. the Dana axle will have a side-ways egg shaped cover with a square hump around the fill plug.

The reason I bring this up about what type of suspension you have, is you are looking at doing a locker and brakes. If you have the leaf style suspension, then you may want to look into a 14 bolt from a 1973 and up Chevy truck. 14 bolt parts are cheaper, and easier to come by. you will also have the option of 2 more gear ratios. 3.73, ad 3.42. you can swap a 14 bolt into the trailing arm set-up, but it will require welding new spring pads and fabricating, or relocating the panhard bar.

Now, if you do have the Eaton, and want to stay with it, The brake swap is straight forward. you will need the backing plate, fully assembled, and the brake drum from a 1973 and up 14 Bolt truck. They are interchangeable as I demonstrated. If you want to use the 9/16" studs, you can simply have the hubs bored out to accept them. the inner wheel seal is the same for the Eaton as it is for the 14 bolt.

On that, the bearings for the 14 bolt and the Eaton are DIFFERENT. The 14 bolt hubs will not swap dirrectly onto the Eaton without machine work for the inner bearing journal to accept the Eaton bearings. But it can be done.

Lockers. You have the option of one locker. The Detroit No-Spin. There is an original factory Detroit that usually sells for 400 and up. Then you have the "other" No-Spin option. The Detroit locker for the 14 Bolt is a direct fit for the differential of the Eaton. These lockers are readily available, and can be had used for around 200 and up. There is one catch to this though Swapping a 14 bolt locker into an Eaton requires the use of the 14 bolt axle shafts, and machining about 0.250" off of the splined ends. Otherwise it is a direct bolt in. I have pictures somewhere of my 14 bolt locker installed in my Eaton. I will have to load them to the computer.

I hope this little bit helps. If you want, post up a picture of your axle if you are unsure what you have.
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Old 02-27-2013, 02:11 AM   #12
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Found them.

That is a 14 bolt carrier on the left, Eaton on the right. I swapped the guts.


Bolted together
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Old 02-27-2013, 09:41 AM   #13
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Mine is basically a round slightly ovate cover on the rear. I haven't looked at the front of the diff, yet.
I'll try to get under the truck with a camera tonight.

Thanks for taking the time and effor to post this stuff. It is really appreciated.
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Old 02-27-2013, 08:22 PM   #14
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Here is a pic of the cover on my rear end.

Next, a pic of the front of the differential.
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Old 02-27-2013, 08:46 PM   #15
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

That would be the Eaton on leafs! the only welding that would be required if you wanted to swap in a 14 bolt would be relocating the shock hangers on the axle.
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Old 02-27-2013, 08:57 PM   #16
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

That would be an HO52 then and very likely the stock axle. Now you need to decide if you want to upgrade the brakes or just put in a locker. Couple of things I would do the help the decision process would to be pull the pumpkin and take a look around and see if it has worn or damaged parts. Rebuild parts exist but are more difficult to find. Another would be to measure the front track now that you have disc brakes and match it to the rear. From the pictures it looks like you gain about an inch on either side swapping brake parts.
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Old 02-27-2013, 11:25 PM   #17
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Thank you Longhorn 70 for posting that picture of an Eaton rear axle. I don't have any that are still bolted under a truck!

Just for reference, I am posting a picture of a Dana 60 from under a 67-72 GM truck. Notice the square part of the cover. This would be how you would differentiate the Dana 60 from the Dana 44. Other manufacturers used 5 Lug Dana 60 semi floating axles under half-ton trucks and SUV's. And I am only referring to back-in-the-day vehicles, not modern ones.

Dana 60


Here are some pictures of a 14 bolt Full float 10.5"

14 Bolt




Anyone have a picture of a stock diff covered 14 bolt? I don't have a straight on one.

SS Tim, you bring up a good point about track width, I didn't even think about that with his new front end! I want to say the TW on the Eatons I have measured have been 67". I will have to double check my notes tonight.
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Old 02-27-2013, 11:54 PM   #18
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

After I get the front end aligned, I'll measure the track width. Do I really want it the same? I remember Pontiac made it a big deal when they had a wider track on one end.
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Old 02-28-2013, 01:20 AM   #19
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

You won't get a factory rear end wider than the front end, I think what SS Tim is talking about is the track width on the rear might be 2+ inches narrower than the front.
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Old 03-04-2013, 08:20 PM   #20
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Thanks. I'll measure once I get it to the alignment shop and get all the same wheels on. They are sitting until I get it aligned.
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Old 03-10-2013, 10:36 AM   #21
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Does anyone know if the hubs from the 2002 & up disc brake with the drum in rotor ebrake uses a different hub than the drum brake equipped 14 bolts? Was looking at buying some like http://www.fourwheeler.com/departmen..._new_products/ from right gear and axle, or having custom adapters made for the backing plates. Hoping to do the 2002 & up disc swap on my Eaton

Edit: Hoping I would be able to use it with the Eaton hubs of course. Just wanted to make sure the drum hubs would work before I go buy some rotors
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Old 03-10-2013, 12:52 PM   #22
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

I believe you are asking this because you want to use the slide on rotors correct? I am fairly certain the 11.5 AAM hubs are way too different. I don't know about the 02+ 10.5 hubs.

This is actually something I have been thinking about doing with my eaton because I don't want to use the Caddy calipers.

One thing for sure is that A backing plate bracket will have to be fabricated and welded to the axle housing.

As for the hubs, there are 2 possible easy routes.
1. Early Eaton axles used slide-on drums, which may work for the 02+ rotors
2. Mid 90+ 14Bolt FF axles used in some Suburbans (for sure, maybe lighter 3/4T trucks and 1 ton vans) used a slide-on drum. For the 14 bolt hubs, read below.

Here is what you need to make the 14 bolt hub work on the Eaton spindle, you will need to use a combination of an inner bearing cone for an Eaton and a Bearing race for a 14 Bolt hub. Then for the outer bearing, you will need to have the 14 Bolt hub machined to accept the Eaton outer Bearing race.

I am not the first person to try this. There are many others who have put the 14 bolt hubs on an Eaton.

edit: I just looked closer at the link you posted... If you enlarge the picture of the 14 Bolt you will see a spacer/adapter that they used to adapt the newer bracketry to the original axle. I am curious to know what they did for the hub/rotor? I checked out their web page and it doesn't say anything about the kit.
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Old 03-10-2013, 03:01 PM   #23
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Talking Re: Eaton HO72/HO52 vs. 14 Bolt FF

Thanks! I sent them an email asking for more details on the kit. Somebody listed the parts needed needed in this thread http://www.pirate4x4.com/forum/gener...all-parts.html

I did not see the hubs listed in the parts list. So who knows? I will update as soon as I hear back from right gear and axle or from the guys on pirate
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Edit: got a failed delivery status to right gears email. I will try to contact them by phone sometime this week when I get a chance.
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Old 03-10-2013, 09:47 PM   #24
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

Ive got a 71 K20 with a Eaton underneath it...4:10 ratio. It is 51 1/4" wide backing plate to backing plate. Is that normal width??? Seems awful narrow.

Also, just curious as to the value/durability of this axle vs. a Dana 60?

Thanks in advance...Alan
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Old 03-10-2013, 11:43 PM   #25
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Re: Eaton HO72/HO52 vs. 14 Bolt FF

That's not the correct way to measure the width of a differential. The correct way is to measure WMS (wheel mounting surface) to WMS. That is the industry standard, and only way to make an accurate comparison between differentials.

Personally I prefer either the 10.5 14 bolt or the Dana 60. However there isn't anything wrong with an Eaton HO52/72 if it is in good condition and has a gear ratio that works for your needs.


Quote:
Originally Posted by My72BB View Post
Ive got a 71 K20 with a Eaton underneath it...4:10 ratio. It is 51 1/4" wide backing plate to backing plate. Is that normal width??? Seems awful narrow.

Also, just curious as to the value/durability of this axle vs. a Dana 60?

Thanks in advance...Alan
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