G506/G508 banjo rear axle outer seal?

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forestry4evr
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G506/G508 banjo rear axle outer seal?

Post by forestry4evr » Mon Apr 10, 2017 8:46 am

Hey all,

The manual states to just set the rear wheel nuts to proper bearing load adjustment and then tighten the outer seal/jamb nut combo and you're done... Okay, flash forward 70 + years working with different modern style cone bearings (although direct replacement KD-12051-Z and KB-11786-Y bearings are used) along with neoprene outer seals (not the original leather seal). How much is the neoprene seal supposed to protrude beyond the hub body so that the proper amount of compression on the axle shaft controls against gear oil migration into the wheel bearings? I would imagine protruding out too much will tear up the neoprene, and of course too little will allow gear oil intrusion.

What distance works? What have you all done? Can the seal/jamb nut be shimmed out if it is too deep in the hub, and if so what material have you used?

Thanks!

Paul
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Re: G506/G508 banjo rear axle outer seal?

Post by Joe Gopan » Mon Apr 10, 2017 11:05 am

Banjo CCKW and G-506 original bearings are called "barrel Bearings" because of their beer barrel shape. Tapered roller are not original, not sure if you have found tapered cones that some how fit or if the outer seals end up in the correct location on the spindle.
I'd stick to the original bearings.
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Re: G506/G508 banjo rear axle outer seal?

Post by D.R.H. » Mon Apr 10, 2017 5:16 pm

Sometimes the 'Barrel Bearings" are very difficult to find.
What Paul wants to know is how far past the profile of the hub is the rear outer spindle nut/seal supposed to protrude? I have found that after installing the outer wheel bearing, 1st. washer, 1st. spindle nut, 2nd. 'spider" washer and then outer spindle nut/seal, the neoprene seal usually winds up protruding out past the hub around 1/8" to 3/16". I believe, from experience, that there is enough lubrication in that general vicinity to prevent damage to the neoprene after the axel shaft is installed.
Last edited by D.R.H. on Fri Aug 17, 2018 7:41 pm, edited 1 time in total.
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Re: G506/G508 banjo rear axle outer seal?

Post by mudflap » Mon Apr 10, 2017 7:33 pm

Sometimes the "Barrel Bearings" are very difficult to find
D.R.H., you're not kidding.... I had to replace several of these on my truck when I first got it. Some were very worn, some had been replaced with conventional Timken tapered roller bearings. (Apparently there are tapered roller bearings available which directly interchange with the original Hyatt bearings.) In any case, I remember looking long and hard for those until one of the guys at a bearing place called someone, who knew another guy, who's brother in law heard of a place...... Anyway, he was able to procure enough of them for my needs, but I nearly had to give him my first born.

BTW, I personally believe, that if these are ultimately unavailable, the tapered roller bearing option would work just fine. I think that the merits of that barrel bearing design are primarily in compensating for any angular or axial misalignment of the inner & outer bearings - something that should only exist when the axle is uber-heavily loaded - to the point where there might be some deflection in the end of the axle tube.

But, alas, I digress....

When reassembling the hubs on my rear axles, (using all of the aforementioned Hyatt bearings), three of the four seals seemed just about right - protruding past the surface of the hub maybe 0.050" - 0.060". Considering the axle shaft gasket is approximately 0.020" thick, this still provides for some compression of the seal when the axle shaft is installed.

However, the fourth seal was actually flush, or maybe a few thousands below the surface of the hub when the bearing nuts were in place. According to the good Dr. Deuce, this condition is not totally unheard of. My solution was to purchase shims from McMaster Carr, open up the ID so they would slide over the axle tube, and place them beneath the bearing retaining nuts - thus raising the surface of the seal.

This process is outlined in the following post: http://cckw.org/forum/viewtopic.php?f=1&t=5195

D.R.H, with regards to the installed height, I am afraid that I must disagree with you on this point. IMHO, 1/8" to 3/16" seems a wee bit high. I would be concerned about tearing up that seal with it being compressed to that degree. (However if, in fact, you have been running this height and all is well, the first round is definitely on me if I am ever in your area :) ).

Lastly, one other thing to check is the inner surface of the axle shaft flange. Two of mine were pretty scored up (long story, click here if interested: http://cckw.org/forum/viewtopic.php?f=1&t=5509 ), necessitating some lathe time to clean up that surface.

Best Regards....

p.s. As mentioned on this site and others, that seal is only used in the military application of this axle. It is not present on civilian applications. Before I thought of McMaster Carr, I was thinking about using a differential carrier bearing shim. I went to the local ring and pinion shop to see if I could purchase some (they were the wrong size) and ended up in a spirited discussion with the elderly technician there who insisted that these axles absolutely, positively, never had any such seal...

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Re: G506/G508 banjo rear axle outer seal?

Post by D.R.H. » Mon Apr 10, 2017 8:27 pm

Mr. Mudflap, Sir. I must first say that your post was definitely well thought out and written. Next, I will admit that at this present time I don't remember how much that seal is supposed to "sit proud" of the hub, it has been a long time since I have had to effect repairs in this area of a Chevy as I sold my first one back in 2012. I was just making a guess to help Paul, and thinking about it now, it was one that was too generous. I concur with your links and measurements and will have access to my 2nd. Chevy in a few short weeks. At that time I do intend on pulling one of the axel shafts to take a closer look and perhaps a measurement or two.
Thanks for posting.
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Re: G506/G508 banjo rear axle outer seal?

Post by forestry4evr » Tue Apr 11, 2017 1:48 am

Gentlemen,

First off thanks very much to the folks that provided some very good thoughtful and technical information. It is clear that you have travelled the very same road I am on at present.

Unfortunately when I got in my DeLorean to travel back in time to purchase some of the barrel shaped Hyatt bearings, I found that the craft was out of plutonium fuel and it was a cloudless moonlit night so no lightening was available. No forward power... bummer! As result, I had to settle with the modern Timken cylindrical shaped tapered bearings. The bearings used are the same part number as the original Hyatt bearings KD-12051-Z for the inner cone/cup and KB-11786-Y for the outer cone/cup. The "modern replacement" neoprene outer seals may be a different height than the original leather seals anyway so the critical distance that the seal protrudes (or should protrude) past the hub is still in question. I wish the original engineers addressed this odd sealing method a little more clearly for folks like us at the present time.

Mudflap, your mention of the shims from McMaster-Carr is spot on, as the same solution came to mind. The ID of the spindle is 2.125 inches, and unfortunately their size selection stops at 2.00 inches. They do carry metric round shims though, and I believe a 55mm (2.165 inch) ID, 68 (2.677 inch) OD shim will fit adequately. https://www.mcmaster.com/#standard-shims/=175d8qv

So here is the question that the responses have had a large degree of variability. How much should the seal protrude past the hub? This issue is something we will need to deductively reason as we are pretty much flying by the seat of our pants. I agree that too tight will kill the seal and too loose will allow gear oil intrusion. So is 0.050 inch adequate or 3/16 inch adequate, or is something in between adequate? My guess is that your SWAG of 0.050-0.060 is on the mark, but I have no real basis for that decision. Mudflap, are your hubs leaking gear oil after your remedy? I put together the passenger side axle bearing assembly last night and determined that the seal stands proud of the hub by 0.030 inch, and the terne plate axle shaft seal is 0.020 inches thick leaving only 0.010 inches of seal pressing against the axle shaft. In my empirical observations, this 0.010 inches is too little seal pressure on the axle shaft as I am repairing a leaking seal failure. The shims from McMaster-Carr come in a variety of thicknesses, so which ones to buy????

Thanks again for your great exchange of information, and I look forward to hearing your input.

Paul
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Re: G506/G508 banjo rear axle outer seal?

Post by Joe Gopan » Tue Apr 11, 2017 5:22 am

The OEM spec bearings will eliminate any guesswork along with eliminating the risk of having the Gear Oil soaking your brake shoes. The newer Neoprene seals of the past 60 or so years are equal in dimension to the original leather. I have never been unable to come up with the correct NOS OEM bearings and races and have kept some on hand in retirement for a loyal customer should they should they need more.
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Re: G506/G508 banjo rear axle outer seal?

Post by Joe Gopan » Tue Apr 11, 2017 2:50 pm

There is a self-aligning feature to the barrel bearings found on Banjo GMC/Chev differentials and rear wheel bearings that contributes to the longevity of Banjo Rear Axle Shafts.
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Re: G506/G508 banjo rear axle outer seal?

Post by rjbeamer » Tue Apr 11, 2017 4:01 pm

Joel my understanding and teaching is that Barrel bearings are only slightly self aligning when used as a single bearing. Not when used in a pair as in double rear axle bearings.

Roger

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Re: G506/G508 banjo rear axle outer seal?

Post by Joe Gopan » Tue Apr 11, 2017 4:56 pm

I see what you mean, my understanding is that there is just enough alignment motion to reduce some of the flexing at outer end of the axle thus reducing metal fatigue. Some 30's-50's GM trucks used barrel bearings.
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Re: G506/G508 banjo rear axle outer seal?

Post by Jan41Cargo/winch » Tue Apr 11, 2017 6:08 pm

Good bearing distributors know these "barrel" bearings as REX bearings named after the original manufacturer.

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Re: G506/G508 banjo rear axle outer seal?

Post by mudflap » Tue Apr 11, 2017 8:39 pm

Hi Forestry-4evr,
Unfortunately when I got in my DeLorean to travel back in time to purchase some of the barrel shaped Hyatt bearings, I found that the craft was out of plutonium fuel and it was a cloudless moonlit night so no lightening was avai
I hate when that happens.... :)

I put those axles back together in 2014. Since then, I have not pulled the hubs apart to inspect for the presence of gear oil. However, I did have the brake drums off last fall and everything looked nice and dry.

As I recall, I purchased a pack of approx. 10 shims, and kept adding them until the height of the seal was in the neighborhood of around 0.050" to 0.60". In order to enlarge the center hole of the shims, I scribed the desired ID on the surface of one of the shims, taped the entire pack together around the circumference, clamped the pack in the vise, and carefully opened up the ID with a fine half round file, followed with some sandpaper to smooth out the burrs. If you are careful, when you are finished it looks like the shim was manufactured that way. I confess, it did not occur to me to scroll farther down the page in the catalog and investigate their metric offerings. :oops: If you can find one that fits (both ID and OD), then I would use it as it beats filing.

0.030 to 0.060" is close to 1/32 - 1/16", which I have seen a quoted a number of times. In your case, if you have only 0.010" after the metal gasket is in place, I would look at shimming it out maybe 0.020" - 0.030" (or the nearest metric equivalent). I too, am running the modern neoprene (or maybe they are nitrile? - not sure ) seals, as I am not a big fan of those old leather jobs.

That seal interface should not be under very much pressure from the GO. If, BTW, I was experiencing chronic issues with GO getting into the hubs, I would check the vents to ensure that they are not plugged.

Hi Ben,
The OEM spec bearings will eliminate any guesswork along with eliminating the risk of having the Gear Oil soaking your brake shoes.
In my case, I was using all OEM spec bearings, and still had issues with that one hub. I understand that this interface is designed to be net build (i.e. no adjustment required), but this does not seem to be the a case 100% of the time. Perhaps the variations in tolerances for machining those hubs opened up slightly under the demands of war-time production. The next time I pull them apart to repack those bearings, I will get out my depth mic and make some measurements.
There is a self-aligning feature to the barrel bearings found on Banjo GMC/Chev differentials and rear wheel bearings that contributes to the longevity of Banjo Rear Axle Shafts.
Correct. That's what I was referring to in my previous post when I mentioned "angular or axial misalignment of the inner & outer bearings". Under severe loads, I would wager that the axle tube is actually bending slightly, moving the inner and outer bearings out of alignment. I seem to recall that the engineering or applications manuals for standard tapered roller bearings have a maximum specification for this misalignment. I'm sure that the barrel bearings, which appear to be distant cousins of the modern spherical bearings, have a much greater tolerance to this. If anybody ever digs up an engineering applications manual for these, it would be interesting to know this value.

I have always heard that the Chevrolet produced banjo axle could take more abuse than the Timken axle. Do you recall what the typical failure(s) were on these? Were they bearing related?

Best Regards...

Bob

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Re: G506/G508 banjo rear axle outer seal?

Post by motto » Wed Apr 12, 2017 1:22 am

The consensus appears to be that the banjo axle is stronger than the split axle. I've seen failures in both. I once purchased a DUKW that had no teeth on the intermediate axle pinion. The area where the teeth should have been was polished blue. The crownwheel had all its teeth but was a little chewed. The rearmost axle had broken a shaft so only the front axle was driving.
I also wrecked a Studebaker US-6 that was used in a quarry, one of the diffs had the nose of the pinion broken off where the support roller mounts.
I purchased another US-6 that had been overloaded to the extent the housing on one of the rear axles was bent like a bow and the wheels leaned in at the top like a swing axle Volkswagen with a heavy load.
(The US-6 has virtually the same drive line as the split diff CCKW)

David

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Re: G506/G508 banjo rear axle outer seal?

Post by forestry4evr » Wed Apr 12, 2017 1:54 am

mudflap wrote:I put those axles back together in 2014. Since then, I have not pulled the hubs apart to inspect for the presence of gear oil. However, I did have the brake drums off last fall and everything looked nice and dry.

0.030 to 0.060" is close to 1/32 - 1/16", which I have seen a quoted a number of times. In your case, if you have only 0.010" after the metal gasket is in place, I would look at shimming it out maybe 0.020" - 0.030" (or the nearest metric equivalent). I too, am running the modern neoprene (or maybe they are nitrile? - not sure ) seals, as I am not a big fan of those old leather jobs.

That seal interface should not be under very much pressure from the GO. If, BTW, I was experiencing chronic issues with GO getting into the hubs, I would check the vents to ensure that they are not plugged.

Bob
Bob,

Thanks for your efforts. As luck would have it, a random search for plate steel at my local scrap yard yesterday yielded the shims needed...Hard to believe, but I happened across the remnants of a shim pack located among some larger modern truck drivetrain parts. The shims fit ID and OD perfectly and include (1) 0.030, (5) 0.010, and (6) 0.005 shims. Should be plenty to build out the seal. Go figure huh?...I should have bought a Mega Millions lottery ticket too as the WW2 truck gods where in my favor!

The barrel bearings were used during a short transition from ball bearings to modern style bearings. As this style died out in the 1950's in favor of the modern column shaped bearings still used today, I am not sure it was a success. It might have been yet another "red herring" GM latched onto much like the babbit bearing Chevrolet engines. GM has a long history of resisting change.

Thanks again for the help!

Paul
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Re: G506/G508 banjo rear axle outer seal?

Post by Joe Gopan » Wed Apr 12, 2017 4:29 am

If the Banjo rear wheel bearings are not monitored for adjustment periodically, and they are driven with loose bearings, the rear axle flanges will not have even contact with the outer seals. The 4X4 Chev and CCKW Banjo wheel bearing adjustment on these trucks are not a "drive and forget item". These have always required more attention than trucks having tapered roller bearings.
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