Eaton HO72 rear axle

[RPOZ11]

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

[RPOZ11]

General update...

Put together this 14 Bolt.
3:42 with an Eaton Posi installed.
Then I realized : DUH
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.

[RPOZ11]

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

[Shaky]

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

[RPOZ11]

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

[RPOZ11]

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.

[RPOZ11]

Axles arriving today
I'll post pics of these asap

[RPOZ11]

Done

[bry593]

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?

[RPOZ11]

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.

[bry593]

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.

[Asshat]

Originally Posted by RPOZ11

Just picked this up
HO72 Detroit Locker rear axle
Drum to Drum
Here is the code and tag from it
Can anyone decipher the stamped code?
R JJG0761

Tag has no info on it

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.

[RPOZ11]

Originally Posted by bry593

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 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.

[RPOZ11]

Originally Posted by Asshat

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

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.

[Asshat]

Originally Posted by RPOZ11

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.

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

[bry593]

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.

[Andy4639]

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

[DeadheadNM]

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

[Andy4639]

Originally Posted by DeadheadNM

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

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.

[DeadheadNM]

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.

[Andy4639]

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.

[DeadheadNM]

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.

[BigBird05]

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

[Andy4639]

Originally Posted by DeadheadNM

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.

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

[DeadheadNM]

Originally Posted by BigBird05

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

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/