Re: Eaton HO72 rear axle
 

Rear Caliper on for test fit:

Re: Eaton HO72 rear axle
 

Carrier, support, & yoke stripped and ready for black powder coat :

Re: Eaton HO72 rear axle
 

Just an update.
Working on rear calipers.
Possibly going to look into reproducing parking brake brackets and springs.
Aftermarket new calipers look ok.
The core GM calipers need some attention.
Powder Coating was delayed; so I'm a week behind now.
Once I can get all this resolved I can then order the axles.
Until then, same old slow process.
Never imagined the cost of doing these.
And I have 2 more to do.
More updates to come...

Re: Eaton HO72 rear axle
 

Yeah - the price on that bearing kit is eye-opening. I like my HO52, but if it ends up needing too much I might have to consider a 14-bolt. Nice work - following with interest...

Re: Eaton HO72 rear axle
 

Well I'm into it deep now.
Goal is to complete it.

Powder Coating :

Re: Eaton HO72 rear axle
 

Side Load Bolt :

Re: Eaton HO72 rear axle
 

So here we have my 14 Bolt axles out sitting side by side as an example of the length comparison/differences.
17-30 spine difference.
Length difference using a straight edge of a bar to show how close they are & how I need to order shorter axles so that they dont hit or become a clearance issue.
Once I get the ring & pinion back from being assembled, I will then discuss further what is necessary with the axles.
Bear with me.
This will take a few weeks to finalize this all.

Re: Eaton HO72 rear axle
 

i am looking forward to an axle comparison. i want to put a 14 bolt locker in my ho72

Re: Eaton HO72 rear axle
 

I hear you. I've spent a lot of money with less to show for it. You're gonna end up with a nice piece (or three). :metal:

Re: Eaton HO72 rear axle
 

This one isn't mine but a similar rear disc swap.
With the vented rotors, the rotor outside diameter was a small bit too much from the manufacturer.
What was happening was that the rotor was slightly hitting the caliper pin.
His remedy was to take off ONLY enough material to keep it from hitting.
In the image below, you will see that he took off more material than was needed but leaving enough surface area to show full contact of the brake pads.

Just an FYI; but I thought it was worth sharing.
Maybe not all rotors have this problem.

Re: Eaton HO72 rear axle
 

Carrier reassembled.
Note now having the 30 spline Detroit Locker installed.
Next, to finish up caliper installation then I can go forward with installing this.
Axles forthcoming

Re: Eaton HO72 rear axle
 

General update...

Put together this 14 Bolt.
3:42 with an Eaton Posi installed.
Then I realized : DUH :dohh:
Spring pad location and shock mounts need to modified in order to install it into a '72 and back application.

So... now I'm off to the welding shop to get a time to get this resolved then re-powdercoat the axle tubes after all is done.

I'm using this 14-Bolt for axle length comparisons prior to completing the HO72.

Re: Eaton HO72 rear axle
 

Slow building these days.
Here are the Hubs assembled and test fitted.
Rotors and studs next...

Re: Eaton HO72 rear axle
 

Thanks for the update. Can't wait to see this finished.

Re: Eaton HO72 rear axle
 

I'll get there.
Had a few expenses slow me up.

When we installed the Timken Bearings,
The 388 race was miss-boxed.
It had a 382-A 14 Bolt race inside the 388 box.
Luckily I had new Timken Bearings present to cross reference this.

So good to check and double check these things

Re: Eaton HO72 rear axle
 

Finally getting ready to order up axles for this.
Below in the image are the numbers I determined for the factory dimensions.
I did measure the depth that the 17 spline axles have.
Installed, taking into account the 17 spline locker, you are left with a maximum 5/8" clearance before the axles actually touch.
I compared my 14 Bolt axles at where they are splined to the original 17 splined axles and both appear to have similar diameters.
The HO72 axles were about .025 larger.
I went with the 14 Bolt size because I am using an Eaton 30 spline locker designed for the 14 Bolt axles.
The 14 Bolt axles were 1.500.
Add:
Axle flange thickness : .390
Axle bearing landing where hub bearing rides : 1.440
I hope these are all correct.
To be splined for 30 teeth.

Re: Eaton HO72 rear axle
 

Axles arriving today
I'll post pics of these asap

Re: Eaton HO72 rear axle
 

Done

Re: Eaton HO72 rear axle
 

I know this thread is a few years old, but just wanted to say thanks! You did a great job documenting what has become increasing obscure knowledge of the HO52/72.

My plans are to transplant an original Eaton no spin / Detroit Locker into my HO52. Which leads to my question, if you had an original no-spin to begin with, why bother converting it to a 14-bolt no-spin?

Again, this is the best documentation I have found. Thanks!

EDIT:
Anyone know if the 1966 and older trailing arm HO52/72 axles share the same perch spacing as 1967 - 1972 trailing arms?

Re: Eaton HO72 rear axle
 

Increasing to the 30 tooth count from the 17.
Stronger and the 14 bolt locker is readily available.
Although the costs to make the axles were a factor, I felt doing this allowed me piece of mind driving with this setup.
I cant imagine trying to locate the inner locker gears mating to the stock spline axles.
Piece of mind I suppose by preserving the original unit.
Ive got one more housing to do a correct rebuild.

Re: Eaton HO72 rear axle
 

I thought you were going to use the Escalade hub seals? I know you had pics of them, but in your "hub test fit" pic above, I'm seeing the old style seal. Was there a problem with the Escalade seals? I ask because I am ordering parts for my HO52 and had planned on the new style seals.

Re: HO72 rear axle
 

Hey, I’m a real noob to these rear ends... I thought the Eaton posilock rear ends were all geared real low, I know mine is. What is the desire to have these in your truck? I thought the Dana rears were a better choice since they are geared taller.
Thanks - hope this isn’t a stupid question. I would be willing to sell mine; hoping I can do that once I get this baby on the road.

Re: Eaton HO72 rear axle
 

I believe I did indeed use them.
Axle is burried at the moment.
I'll have to double check that, but as my old memory recalls...I thought I used them.

Re: HO72 rear axle
 

They are geared low.
I believe mine is a 4:11.
Originality.
Decided to run the HO.
(I have an extra HO drum to drum)
Gear Vendor will assist in my highway mileage ; but probably not enough.
I think there was a 3:90 gear GM offered; or something like that.
Can't recall the 3 series ratio.
Very hard to locate those.

I have a 14 Bolt that I considered using.
3:42 posi in that one.
Just need to move and install spring pads correctly onto it in order to use that one.

Re: HO72 rear axle
 

I also read somewhere that they make the tires chirp when turning, is this an issue to be concerned with?

Re: Eaton HO72 rear axle
 

Lockers will make noise, cause poor handling (understand) and accelerate tire wear. They are a terrible addition for a street driven truck. On the other hand, if you use your truck as a truck, towing things and hauling through fields and mud, a locker is a blessing.

For good handling on street you want limited slip (actually does slip). These never lock completely and one tire will usually spin faster than the other. These are a best fit to most motorist driving styles. These are not available for HO52/72.

Re: Eaton HO72 rear axle
 

Hello RPOZ11,

I'm loving the info you have posted here. I have this same rear end in my 67 Ramp truck. Per say by the numbers you posted, except mine has no tag with it.
I'm trying to decide which way to go on the rear E brakes. I have none of the parts for them for it. I'm guessing from your info finding them will be a job in it's self.
With that being said do you have the info for the disc brakes you used and do you know of any full kits with the E brakes as well. I know you posted about making up a E brake spring. Any and all info is appreciated on this. Thanks:chevy:

Re: Eaton HO72 rear axle
 

The tag denotes the presence of a NoSpin locker. It's akin to a posi axle tag.

Re: Eaton HO72 rear axle
 

Yes I understand that. Mine has no tag but who knows it could have been torn off removed by a PO. I doubt it is but the numbers match. So it's a 50/50 chance which would be nice if it where.
I'd like to find the park brake parts for it and leave it as it is. :chevy:

Re: Eaton HO72 rear axle
 

FWIW I just got a box of new internal drum parts including the parking brake for my 72 leaf spring HO52 just in case they’re needed down the road. I’ll post back the part numbers in case they are helpful in any way. There’s a code somewhere on the axle that’ll specify if originally assembled w a locker. It contains a letter but I’m foggy on the details.

Re: Eaton HO72 rear axle
 

Thanks, any info on the park brake stuff is great. All I have in the truck is the brake handle. That's it. I will have to figure out a way to get the cables made long enough for the Ramp truck bed. I'm hoping a 18 wheelier shop can make me some cables if I supple the measurements. :chevy:

Re: Eaton HO72 rear axle
 

Here are some recently accumulated spare parts that I believe are correct for the original HO52 in my 72 K20. Would hate to discover otherwise years from now so please chime in if anyone believes otherwise. It seems the wheel cylinders differ between coil and leaf rear ends.

LH/RH drum internals, LH/RH wheel cylinders, wheel studs, and drums. Hoping the photos show the p/n’s well enough. The new pieces are from NAPA. Regrettably some are PRC made.

Re: Eaton HO72 rear axle
 

Does it matter what size brakes you have? Are all E-bakes parts for HO52 and HO72 the same?

Re: Eaton HO72 rear axle
 

Thanks,
I will take pictures of the parts #'s and see what I can find also.:metal:

Re: Eaton HO72 rear axle
 

The answer is, “Depends”. Some components (spring for example) are common to 1/2t, 3/4t, and 1t axles. Other pieces (brake shoe lever for example) exchange for 1/2t and 3/4t but not 1t. Note the left park brake shoe lever for a 72 ser20 4wd doesn’t exchange for other year 4wds but does with 67-69 Ser 20 2wd, 70-72 Blazers, and Ser 10 2wd 56-72.

Andy, it’s a minefield in terms of parts selection to be honest especially for a 72 4wd rear and C30 with the differing capacities. IMO you’d be well served with a copy of the parts manual. The parts can be had and often inexpensively. I just saw outer bearings NORS USA made for $7 ea or best offer; pinion felt seal NOS GM for $10 shipped. You’d probably save yourself enough cash to recoup the expense of buying a parts manual by buying old stock versus buying new parts.

Torque King 4x4 may be a helpful parts source too: https://torqueking.com/category/1967...052-rear-axle/

Re: Eaton HO72 rear axle
 

Dumb question but I have to ask.

How do I know what year the rear end is? I have no idea. This truck is pieced together from different years. Is there a mark on the rear end some where are does the numbers I posted give me my answer. It looks like they are all the same for our models. Mine having the load bolt helps. What parts manual do I need to look for?
Thanks for all the info so far. :chevy:

Re: Eaton HO72 rear axle
 

Look here for axle ID information: http://67-72chevytrucks.com/vboard/s...d.php?t=590959

The parts are out there. It just takes some sleuthing but that keeps things fun - like hunting. Here’s the manual I’ve made use of:

Re: Eaton HO72 rear axle
 

$200.00 for a manual! I guess I need to do some searching.:chevy:

Re: Eaton HO72 rear axle
 

How about a free electronic version then? Buy Ron a beer sometime :)

Link: http://67-72chevytrucks.com/vboard/s...d.php?t=817560

Re: Eaton HO72 rear axle
 

Andy4639 :

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