Please verify Differentals 72-3/4 4x4

[4x4Poet]

Originally Posted by budbeater

...That brings me to a question. (4X4Poet you posted alot of info about part numbers for a rebuild so you might know this.) I am going through a NAPA dealer for my axle seals and bearings. Is there any upgrades that I can do in the seals and bearings department that anyone is aware of? Does anyone have part numbers?...

I posted above that tapered bearings and races are available for H052 hubs. AFAIK, the original H052 hubs in my '71 & '72 trucks came with barrel roller bearings that are inferior to tapered bearings. My '72 K20 has tapered bearings already. Back in '94, I replaced the barrel roller bearings in my '71 K20 burb's H052 with new tapered bearings. My local bearing sales cross referenced the barrel roller bearing part numbers to tapered after I brought them in. They might have used the app, as well. But they did cross ref the part #s too, perhaps for surety. Worked great.

Don't know the part numbers. Timkin stuff.

[4x4Poet]

Originally Posted by roger0080

...This thread answers a lot of questions just after I started this thread:
http://www.67-72chevytrucks.com/vboa....php3?t=174664...

That thread has some good Eaton H052 info worth quoting here:

Originally Posted by roger0080

...I am all confused when looking at the GM parts book and online parts sites (www.rockauto.com, www.federal-mogul.com (AKA wagner) etc) as to what would interchange on which axle and what is ACTUALLY on the axle.

From What I can tell (Eatons ONLY; not talking about Dana's):
67-72 C20 2WD Eatons have 11-5/32x2-1/2" shoes
67-70 K20 4WD Eatons have 12x2" shoes with 1/2" studs
71 C20 2WD Eatons have 11-5/32x2-1/2" shoes with 9/16" studs
71 K20 4WD Eatons have 12x2-1/2" shoes with 9/16 studs
72 C20 2WD Eatons have 11-5/32x2-1/2" shoes with 9/16" studs
72 K20 4WD Eatons have 11-5/32x2-1/2" shoes with 9/16" studs

Q: GM parts book lists the hubs as different between 67-70 & 71/72 so I suppose
that means 1/2" and 9/16" studs respectively in those years?

Q: According to the GM parts book, all 67-72 4WD 3/4Tons have the same backing plate. How does a 11-5/32" drum fit on a 12" backing plate?

Q: Whats the difference in the drums between a 71/72 C20 and a 72 K20 drum ?
Books say these are all 11-5/32" drums yet give 2 numbers for 71/72 C20 & 72 K20 drums and 2 different prices:
71/72 C20 drum $110.00 non-finned
72 K20 drum $55.00 finned;...

[4x4Poet]

hehe!

Only I could stretch an Eaton thread to two pages on the 4x4 forum.

[Best Elvis voice]
Thankya, Thankyaverymuch!
[/Best Elvis voice]

[budbeater]

OUtstanding information. I appreciate the time you guys have taken. This thread should reach FAQ status soon.

I visited my NAPA shop today (the guy there can find ANYTHING) and it looks like they stock all the bearings and seals. Now I am just waiting for the kit and the weekend.

Budbeater

[roger0080]

Thanks for the replies.
I dug into this further.
I have looked at a 1972 GMC Parts Manual & 1972 Canadian GM Parts Manual.
The GMC manuals is fabulous. There is no question about what axle they are refering to. They explicitly label the part as HO52, HO72, Spicer 60, Spicer 44 etc.
The GMC manual also gives dimensions on the drums, hubs for 67-70. No 71 & 72 though. Bummer.

I tried to double check the backing plate and the wheel cylinders.
Here is what I found on that:
Backing plate and Wheel cylinders confirm each other:
1967-1972 C20, 1972 K20: all have the same backing plate and wheel cylinder part number
1967-1971 K20: all have the same backing plate and wheel cylinder part number

Hubs:
1967-1970 C20,K20: all have the same hub part number
1971-1972 C20,K20: all have the same hub part number

This is what the difference between 1967-1970 C20 and 1967-1970 K20 Drums are (72 GMC Part Manual):
1. Width of where the shoe pad makes contact with the drum
C20 is 3-7/64th's wide and K20 is 2-13/32nd's wide
2. Width of drum (from insides)
C20 is 4-15/16" and K20 is 4-23/32" deep

I cannot find any references that there is/was a 12x2 drum for 1972 K20's.
I believe 4x4Poet your K20 with the 11x2.5 drums is legitimate.
I think your 71K20 Suburban should have 12x2.5 drums (71 was an oddball year). They may look like 2" unless one is super diligent when it was apart.
Your 2WD wheel cylinders that fit your 72 K20 now makes sense based on the above.
Which means the symmetrical wheel cylinders are for the 12x2 drum backing plates and thus you can't mix the wheel cylinders and backing plates. I'm going to guess C20 is 3/16" brake line and K20 is 5/16" brake line.
IIRC, my 71 K20 12x2.5 drum backing plate had symmetrical wheel cylinders (if I understand that right) and 5/16" brake lines.

If 12" drums for 1971 (1972?) are not available, I see over at rockauto.com there are some 67-70 12x2 (1/2" stud holes) available. I wonder if one could drill out (carefully) the 1/2" holes to 9/16" holes ! ??
Last minute thought, 67-70 hub opening in the drum is 4-19/32nds. Have to check that against a 12x2 drum hub opening.

Hope this helps someone. If not, it's intresting reading!
-Roger

[roger0080]

Follow up:

I am confused in that: Is someone saying that they do in fact have a 12" backing plate with a 11x2.5 drum on their truck????

If not, then when I swap to a C20 setup, I will have to figure out how to plumb 3/16 wheel cylinders to a 5/16" brake line. Hmmm.

Did someone say disc brakes? Heh.

[zimmm]

To adapt 3/16 lines to 1/4" whl cyl, use Weatherhead fitting #7818 available at your local NAPA store.

My 72 K20 has 1/4" hard brakelines from the m/c to the rear hose and from the T on the axle to each wheel cyl., which I believe is what is on your 71 K20. 1/4" lines will use a 7/16 wrench, while 5/16 should use a 1/2". 5/16 is normally used for tranny lines & sometimes fuel lines. Sykyjacker hose for this app was incorrect as it supplied a T for 3/16 hard lines. Just went through this with mine trying to convert it completely to SS lines as started by PO.

[4x4Poet]

You've got to be right on the brake lines, zimmm. I've got 1/4" lines too. I thought they were 3/16 when I was given the choice here between 3/16" and 5/16". I knew they weren't 5/16", but didn't caliper them and didn't know a 1/4" line takes a 7/16" fitting. Thanks for clearing that up.

[toddol1971]

If anybody wants to know how tough the eaton rear end is, just take a look at the current fourwheeler mag. It has an article about the tough truck challenge. 2 guys are running locked eatons. nuff said

[1967k30]

Has anyone ran disc's on a 70" wms Eaton? I have disc's on my 65" wms one but the wide one is an inch wider between the hub and the bolt face where the backing plate attached. I assumed I would just use some washers and longer bolts to make it work but was wondering if anyone else had used one of these?

[1969 GMC]

Originally Posted by 1967k30

Has anyone ran disc's on a 70" wms Eaton? I have disc's on my 65" wms one but the wide one is an inch wider between the hub and the bolt face where the backing plate attached. I assumed I would just use some washers and longer bolts to make it work but was wondering if anyone else had used one of these?

From a dually?
Interesting to learn, I also have the 65" version, and was wondering if there was a wider one.

[1967k30]

It's from a box truck and happened to have a No-Spin in it.It was a dually but I think all box trucks have the wide one.I have some more box trucks located but have not had time to inspect them.Actually I have 63" wsm hubs on it to get a 67 1/2" or 68" wsm. The 63" wms ones were in dually's and older trucks like pre 60'?.They were narrow in the dually's because they were all CC trucks back then.

[4x4Poet]

Another thread reminded me that I found H052 hub washers at the chebby dealer. I'm speaking of the two hub washers that have a tab on the inside circle and slide onto the spindle to either insulate the bearing from the lockwasher or the locknut from the lock washer:

3663658 Washer $5.25 each.

Be sure to take an old one with you (never stake your life on my parts info ). Have a good look at your lock washers, too, since the dealer likely carries them, as well. I found that local auto parts stores couldn't source them.

[MrBinAz]

really enjoyed this thread and.....not trying to jack this thread.....
I have an Eaton H052 and am having some prob's.....
see my post here...http://67-72chevytrucks.com/vboard/s...77#post1447677

[budbeater]

Sorry to resurrect this old thread (but I guess it isn't too old).

I am still in the middle of a disk swap on my Eaton 52. While I have had it apart I have made some armor (a rock ring) for the diff cover since nobody else makes one that I could find. I would love to throw a locker into the mix while I have it apart, but I am a little at a loss. I keep seeing "NO-spin" mentioned. Where can I get something to lock the rear? Are there any new options or am I stuck with old parts. Does anyone have something they want to get rid of?

Budbeater

[drink2mny]

1st off sorry I haven't responded quicker to this thread. ( I am still deployed overseas till FEB)

Thank you 4x4poet for mentioning our company.

Also, thank you Budeater for going with us.
Try to get in touch with Randy again at Blackbird's. He has some connections to eaton lockers, sometimes.
He also gets a hell of a discount on products from Randy's Ring and Pinion.(below cost and will drop ship it to your address) Blackbird's doesn't make any money off the items he gets through Randy's Ring and Pinion.

Again thank you for going with us.

[budbeater]

I have been documenting my swap to rear disks using the blackbird kit. I have a ton of pictures and hope to make my experience into a FAQ thread for others to enjoy.

I have been amazed by how stout the Eaton is. If I remember I measured the axles at 1 5/8". Big bearings, thick everything. It is definetly worth the effort of upgrading and keeping.

BBB

[1967k30]

Budbeater: You can get a 14bolt Detroit and install it along with 14 bolt shafts.That's the only other option other than a factory No-Spin.I haven't done it yet but probably will sometime just to try it.I have a No-Spin already so that's why I haven't done it yet.Randy's would be high $$$$ if they have a No-Spin.You can get a new 14bolt Detroit for $375.Got any pic's of the Rock Ring? I was going to build one but haven't started yet.

[budbeater]

This is a picture of the rough shape of the ring. I have cut a relief for the fill plug, and I am in the process of fine sanding the whole deal so that I can get it chromed.

The ring was plasma cut out of 1/2" plate and the center piece is a little thicker than 1/8". The center band is welded on the inside and the outside and I'm grinding and polishing the welds so that it will look like the ring is a solid billet unit. I had to hand (hammer and some channel iron) bend the center band since I don't have a bender. The bend came out very smooth and even.

Budbeater

[wibilly]

i just started a 71 3/4 ton 4wd with a ho52. it has 12x2'' breakes i know at the very least i need a left side backing plate and wheel cyl backing plate rusted out and been patched with blue rtv and cyl seeping havn't tore in it yet but my question is anyone ever hear of 2.08 gears in one of theasethat is what i come up with by jacking it up and spinning it over. never heard of such a ratio in a old 3/4 ton 4wd but front come out to be the same i know this truck has seen many changes over the years [frame shortened cab replaced] and several engine trans combos] differentials both have blue rtv for gaskets but i was not aware that gears like this were even available for the ho52 anyone ever seen thisi have only came across gears like this in later model military diesels

[roger0080]

I am just guessing in that you are doing it wrong. With an open the diff the rev count is off by a factor of 2. When you spin an open diff and count all the revs, you either have to divide it by 2 or multiply it by 2 I cannot ever remember which.

So just playing here, if you figure 2.08 is the ratio; then 2.08 x 2 = 4.16 or really, a 4.10 rear end. Which is very popular for that axle. That's my guess.

[budbeater]

Originally Posted by 1967k30

Budbeater: You can get a 14bolt Detroit and install it along with 14 bolt shafts.You can get a new 14bolt Detroit for $375.Got any pic's of the Rock Ring? I was going to build one but haven't started yet.

Aren't there three ring gear sizes for the 14? Which one is right for this conversion?

BBB

[1969 GMC]

Originally Posted by budbeater

Aren't there three ring gear sizes for the 14? Which one is right for this conversion?

BBB

There are 3, the 9.5", 10.5", and the newer 11.5".

The 9.5" is semi-float, you don't want it.

The 10.5" is the one you want. FF, 30 spline shafts. The innards look almost identical to the Eaton.

The 11.5" is in newer HD trucks, I don't even think there are aftermarket lockers available for it yet.

[budbeater]

1969 GMC: Escellent! Thanks!

Budbeater

[COBALT]

I'm adding an augmented version of 4x4Poet's part list here after running out and getting all of the parts for my HO52 this morning from Napa.

The items in black is what I bought. The items in red are no longer in their database (but there are new alternatives listed above the items in the list). The items in orange I didn't need to search for because Napa had an equivalent.