my eaton ho whatever has 4 spiders & 5200# rating

[crew70]

whats up with that? I have taken apart 2 stock 3/4 ton 4x4 eaton rear ends and acording to what I lurned on the board they should have a 5200# rating on the tag and two spider gears to be a ho52. mine are 4 spider eatons and the tag says 5200# rear. 4spider should be a ho72. I must be missing something? any thoughts?

[Fast68Chevy]

GM says: the 5200 and 7200lb capacity truck rear axles are of the full floating type with hyphoid ring geasr and drive pinion. the full floating construction enables easy removal of the axle shafts without removing truck load and witohut jacxking up the axle. the diff carrier is heaviuly ribbed to provide rigid support for the diff assembly- differential caps are doweled to the carrier to assure perfect alignment.

the straddle-mounted drive pinion is supports by two opposed taper roller bearings,. the pinion rear bearing is a roller bearing assembly consisting of an outer race and roller asembly- a precision ground diameter on the pinion pilot functions an inner race.
a thrust pad mounted on the end of an adjustable screw threaded intot he carrier housing limits deflection of the ring gear under high torque conditions.

basically the two axle assemblies are identical with the exception of drive gear ratios and brake assemblies(h072 has larger brakes than h052) however some vehicles utilize a two pinion diff while others use a four pinion diff.

wont get into the 11,000lb one, its different alot.


brakes is quickest way to twell if you have an h052 or h072

11x 2 3/4" are h052
and 13x 2 1/2 are h072

so theres how to tell really, but even so GM put only 52 under 3/4 ton and 72 under 1 topn, no exceptions, no optional way to get a 72 under a 3/4 or a 52 undr a 1 ton, so., and all the 72 were welded up fvor use with leaves, no coils ones

[Patrick Sullivan]

I am REALLY confused now.

I just got my truck back (read about that in the thread I'm about to start..), and the plate says 5500 rear axle max. That means it should be the Dana 60, right? But it's an Eaton, with 4 spiders. And coils. The numbers on the axle match up with the HO72.

[COBALT]

Same with mine. My numbers don't indicate it's an HO52 either, rather an HO72. I think the "no exceptions" clause is a bunch of crap. The evidence is right under my LWB bed in the driveway. My GVW is 7500lbs, too.

Fast: the dimensions you read off...what are those for again? Brake drums? What?

[Fast68Chevy]

you still have a h052 if its a coil spring truck and was 3/4 ton from the start with 7" frame rails, i gave brake dimensions per gm info in the overhaul manual from 71, if you lok in any of these six years' factory data books you will see that 52 came in 3/;4 and 762 came in 1 ton,
measure your brake drums,
i shouldnt even be in this thread trying to tell you what GM did, im wasting my time,,

[Patrick Sullivan]

This is really bothering me, so I grabbed a cloth tape measure and got the circumference of the drum (the smaller part next to the wheel, not the larger inner lip, right?). Came to around 41", which gives me a diameter of ~13.05".



Are we measuring the inner or outer part of the drum? From where to where?

[Fast68Chevy]

youre supposed to measure inside diameter,....... you guys need ot check the GM info out before being bent on what you think you have under your trucks, im not sure why i care so much,....
the casting of them all are identical, theres no way to tell form outside, the only thing different is leaf or coil, IE., 1 ton or 3/4 ton, IE., 72 or 52
im done messing around with this with ya,
good luck !

[Patrick Sullivan]

Okay.. anyone know how thick the walls are on the drums?

I am not trying to be stubborn or anything, I am just trying to figure out why 1) My Eaton rear end doesn't conform to the rear max weight that it is supposed to have, and 2) Why the numbers on the axle tell me it's something it's not.

You've actually been quite a bit of help to me, at least, but..

[COBALT]

OK, this is silly. Nothing personal Fast, but first I don't know why you do care so much. Sorry pal, but that's your issue. If you don't want to confer with us lunkheads, then don't waste your time. I don't even know why you said that.

Second, the reason we're all standing around scratching our heads is because the codes GM maintain tell us (at least me) the axle is not an HO52. So my choices are to believe the codes that tell me its an HO72, or to believe that coil suspension + 3/4 ton + drum ID makes it an HO52.

Which set of criteria do we go by to determine what these axles really are? Which is more in authority here: the codes or the configuration?

Fast, if you're telling us to ignore the codes and go with the way the axle is configured then tell us why that criteria takes precedence. If we knew that then we'd all be less stubborn.

I'm done.

[Mike C]

I have NEVER had any luck with the GM axle codes. Take the cover off is the only way to know for sure, especially after 30 years of parts swapping, repairs, and rebuilds. We all know in THEORY what GM would do, and these posts have been very enlightening for me. I have never measured the Eaton axle in my Sub as I am not much interested in it since I have (3) 60's that I AM interested in. I do however like to know what I've got and am interested in you guys following up on this. It could be that GM had a shortage of 60's in a particular ratio/GVWR rating and used HO 72's for awhile to fill a void. Everyone talks about "their" truck, but doesn't specify year. Since Randy's book is a 71 could it be everybody else has a 72? Not sure but could be a factor. Let's keep this thread going to will get some real answers as so many of the others are just REPEATS.

[crew70]

Ok I think I got it.
ho52 and ho72 carryers are for the most part the same.

the only dif is the size of the brakes.

this is messured buy the inside diamitor of the brake drum and the width of the pad.

I have 2 rear end apart at this time and they both are 11" drums but one has wider pads and drums.

I think there is going to be some variances from year to year and its not an exact science..

I work in a mfg plant and we(for example)have 2 different high pressure washer pumps with the same part #. and there totaly dif. our parts books ar not even close on alot of times ether.good thing is we have a good servis department to help the costomers. we are not gm but we are in 7 countrys around the world . I dont think you can expect GM to have every think documented perfectly.

what Im trying to say is I think this is as close as we are going to get.

thanks guys ! OH and you to fast.ha ha
nobody waisted my time .

[roger0080]

This is quite an interesting thread.

1. You could have an HO52 axle housing with an HO72 3rd member I'ld say because over 30 years and previous owners, maybe your original HO52 3rd member was trashed and was replaced by an HO72 3rd member that was available at that time (ie. more plentiful and available than it is now). Since the axle stamp code is on the 3rd member, that would explain the mismatch in axle code to brake drum size and axle tag mismatch. IF you still have the axle tag on the rear cover, that would make sense since you don't need to take the rear cover off to replace the 3rd member.

2. I think the break drum inside diameter is going to tell you whether it is an HO57 or HO72. I have the GM parts book and looked at all this in the past and don't "recall" diffrences in the carrier. I was looking for differences in the carrier because I was interensted in the NoSpin diff and they where both the same carrier/housing part numbers.

3. Here is another kicker. For 1971 3/4T 4x4's *only*, the standard drum size is 12" x 2 1/2". This is a hard to find drum if you want new ones.

After 30+ years, we can be driving around trucks that no-way resemble what GM put together originally!

-Roger

[71BBK10]

how can something have 2 or 4 pinions? the only thing called a pinion is the gear that the driveshaft and yoke hook up to, that i know of.

[Fast68Chevy]

roger is on the ball! alot better explanation than i can come up with right now regarding this,


52 is what factory put in on 3/4 ton and 72 is what factory put in on 1 ton, period, roger has explained a good possibility here, and all the carrier castings themselves are same but codes wouldnt be

71bb, yes these could have either 2 or 4, you should see how many are in the larger trucks, we arent talking actual pinion gear, we are talking the shaft that locks spider gears into the carrier inside the housing you cant tell form outside how many are in it until you pull off the removeable carrier front assmbly

and 69 new, dont think that i am trying to be stupid or smartass towards you or anything,. just am trying to explain to you about this, is hard to explain without ability to show emotion on here,

[COBALT]

Well, it is certainly possible that a wrecked 3rd member caused a swap-in of an HO72. Like some have said over 30 years of driving anything is possible.

This whole thread is probably trivial anyway 'cause people generally swap these out rather than maintain them.