Why have an inner seal on FF?

[ntsqd]

Since this got resurrected I'll also report that the trailer below has another 2+ years of sitting and use with those same exact 3-3.5 gallons of gear lube still inside. Seals are dry, wheels are dry. Same is also true of my 60's FF, but that's been all sitting as the engine swap was stalled by life's events, the trailer sees regular trips to the metal scrap yard.

...

Occurred to me that the trailer that a friend & I built supplies supporting evidence that the hub seals will be fine partly submerged in oil.

Note the D60 wheel hubs. What you can't see is that the spindles were cut off of the D60 housing (square spline shafts were also cut off the flanges) and welded into a large OD tube, which has fill and a drain port in the center (fill cap has a vent hose extended up as high as it could go). There is something in the range of 3-3.5 gallons of 90wt. in that axle tube. When first filled it weeped a little from one of the seals, but since then the trailer has been to Bend, OR and to San Felipe, BCN along with many trips to the dump and a couple to the desert. Long ago the weeping stopped and the axle has been dry on the outside ever since.

 

[Tapage]

and you are using 75W-90 .. right ?

 

[astr]

I'm using Walmart Supertech 80W-90.

 

[lostmarbles]

As promised, I am reporting back after removing the inner axle seals. As I originally stated, I did NOT pack the bearings with grease but am depending on the gear lube from the differential to keep the bearing oiled. 15K miles later and no problems. Most of the driving was highway driving of which at least 3K involved heavy towing (another FZJ80 on a tow dolly, military trailers, construction equipment, etc). I decided recently to fix the parking brakes so I had a chance to inspect the bearings. There was no significant change in bearing preload from when I assembled the axle. There was no sign of any leakage past the big seal. The outer bearings looked like new. I did not pull the inner bearings as that would have required removing the big seal which probably would have damaged it. All back together with original bearings and seals.

Experiment continues!

... I would still never consider following your lead in doing this ...

(Owning two landrovers in my youth with oil-lubed wheelbearings made me recognise what I wanted to avoid!)

 

[watrob]

If I could I would put more baffles in the axle tube to stop the oil working its way past into the bearing.

 

[astr]

... I would still never consider following your lead in doing this ...

(Owning two landrovers in my youth with oil-lubed wheelbearings made me recognise what I wanted to avoid!)

I'm not suggesting this for others. I'm just trying out what all Dana FF axles have used for years. This is not a new concept but has been around for years. I just want to see if it would work on the Toyota axles. When I first asked the question as to why I needed the inner seals, I never received a response that was satisfactory so I decided to try it. I hardly consider this experiment over as 15K miles is hardly a thorough test.

If I could I would put more baffles in the axle tube to stop the oil working its way past into the bearing.

The bearings are now entirely dependent on the oil that comes from the differential via the axle tubes to stay lubricated.

 

[Dieseler]

I'm curious if the bearings are getting sufficient oiling and if you get water in the diffs will all the contaminated oil come out of the axle tubes when changing out the fluid.
I have not seen the inside of the axle tubes on a FF even though I have a couple of them on my rigs I am thinking out load is there enough space for the fluid to flow through from the diif to the axle ends and slop around as required to keep everything well lubed and not overheating the fluid in the ends with the bearings.

 

[watrob]

Yes water does get in the diffs and can contaminate the oil in the bearings. If you watch some of the videos on axle rebuilds they pack Moly grease (black) on the inner side of the oil seal (diff side), to help prevent the diff oil getting past the oil seal, you use Moly in the front knuckles as well. The grease used for bearings is usually red (a high temp wheel bearing grease).

The oil seal in the axle housing are there for a reason as is the oil seal on the backside of the hubs, if oil gets into your hub its only a matter of time before it comes out of the back hub seal and the longer your hubs (front or rear) don't leak the happier you are because its a dirty job rebuilding them.

 

[Fromage]

Andy, good on you for actually trying this in some sort of empirical measurable manner. American trucks have had oil bath hubs in full floater axles for nearly a century and it's a very reliable system that's nearly identical to what's in the back of a Toyota. The axle to spindle clearance is about the same, the bearings will flow a good amount of oil, and the hubs will hold a lot of lubrication when the axle is filled up to the fill plug. Think about it, the whole hub is half full of oil. Also, if an oil seal starts to leak, you'll have a heck of a lot of warning before the level drops enough to affect lubrication, not like greased hubs.

With all heavy duty trucks and trailers in NA, as soon as you see an axle over 7000 lbs or so, it's an oil bath, except unit bearings... Which are sealed.

 

[ntsqd]

... I would still never consider following your lead in doing this ...

(Owning two landrovers in my youth with oil-lubed wheelbearings made me recognise what I wanted to avoid!)

I really think that you need to consider what you're basing your thoughts on. Only the English could design a mechanical pencil that leaks oil. I saw this in a brand new multi-hundred thousand dollar Lola Sports Racer that I worked on. Great dry sump oil pan design, appallingly pitiful execution. It was so poorly made that we never did stop it from leaking oil. A good friend of mine often tells me that the reason that he learned technical Spanish is because he drove a Series II thru Mexico. If he hadn't learned he'd have never gotten the parts he needed to make it home. So how LR does or doesn't do something means nothing to me. They're not a std to judge anything by.
How Dana & Sterling & AAM, not to mention the heavy truck axle mfg's, have been successfully doing something for multi-billions of total miles means a hell of a lot more.


I doubt that this experiment will convince anyone determined not to veer from the OE design. That's OK by me. Do what you want. For those willing to consider other options, that the just might be other, equally good ways to do something this is worth looking at.

 

[lostmarbles]

I really think that you need to consider what you're basing your thoughts on. Only the English could design a mechanical pencil that leaks oil. I saw this in a brand new multi-hundred thousand dollar Lola Sports Racer that I worked on. Great dry sump oil pan design, appallingly pitiful execution. It was so poorly made that we never did stop it from leaking oil. A good friend of mine often tells me that the reason that he learned technical Spanish is because he drove a Series II thru Mexico. If he hadn't learned he'd have never gotten the parts he needed to make it home. So how LR does or doesn't do something means nothing to me. They're not a std to judge anything by.
How Dana & Sterling & AAM, not to mention the heavy truck axle mfg's, have been successfully doing something for multi-billions of total miles means a hell of a lot more.


I doubt that this experiment will convince anyone determined not to veer from the OE design. That's OK by me. Do what you want. For those willing to consider other options, that the just might be other, equally good ways to do something this is worth looking at.

Well said ntsqd..

But behind all this is the fact that the wheel bearings on a Land Cruiser rear full-floater will often last a lifetime with "the OEM grease-lubrication" and minimal maintenance. So what do you really aim to gain by converting them to oil-bath lube?

And in the event that you do happen to get excessive bearing wear (due to grease contamination from a deep water crossings, or due to a workshop stuff-up that applied excessive preload, or whatever else) then with grease as the wheel-bearing lubricant the movement/play at the big seal lip (on the rear of the hub) isn't going to instantly soak your brake linings in oil.

Toyota went to more trouble and cost to lube the wheelbearings differently (with grease rather than oil) so I suspect those Toyota engineers would agree with me...

 

[watrob]

Well said ntsqd..

But behind all this is the fact that the wheel bearings on a Land Cruiser rear full-floater will often last a lifetime with "the OEM grease-lubrication" and minimal maintenance. So what do you really aim to gain by converting them to oil-bath lube?

And in the event that you do happen to get excessive bearing wear (due to grease contamination from a deep water crossings, or due to a workshop stuff-up that applied excessive preload, or whatever else) then with grease as the wheel-bearing lubricant the movement/play at the big seal lip (on the rear of the hub) isn't going to instantly soak your brake linings in oil.

Toyota went to more trouble and cost to lube the wheelbearings differently (with grease rather than oil) so I suspect those Toyota engineers would agree with me...

I agree with Lostmarbles, and like I said earlier, If I could I would put more baffles in the axle tube to stop the oil working its way past into the bearing.

If you have grease in the bearings you don't need oil from the diff as well?

 

[roscoFJ73]

The current system works well.
I cant see why anyone would want to change it just because Landrover or Dana axles are different.

 

[ntsqd]

I laid out in my first post in this thread what I will gain from no inner seals. I will be slightly narrowing and moving the diff to the center of an FZJ-80 housing, so the minimal potential for oil on the brake linings isn't a big concern for me. What I gain is the ability to have axle shafts made more economically by not having to have the sealing surface for the inner seal on the axle shafts. They would be a large deviation from what the axle mfg's are used to making and the opportunity for error and increased cost are significant.

FWIW most of the bearing pre-load stuff-ups that I've seen (or done) have been too little pre-load. My 4x4 mentor once told me "Thom, those are big bearings. You're going to have to work to make them too tight, but too loose is easy to do and will cost you a spindle from an inner race spinning on it."

I've long pondered why Mr. T went to the added trouble of using grease. The only thing that I can find for certain is that it makes both axles the same in terms of bearing maint. and reassembly. I see no advantage, either way, in the case of water contamination.

 

[Fromage]

The current system works well.
I cant see why anyone would want to change it just because Landrover or Dana axles are different.

I think Astr wants to change it because repacking wheel bearings sucks and because he doesn't particularly like doing it.

 

[astr]

The current system works well.
I cant see why anyone would want to change it just because Landrover or Dana axles are different.

Do really enjoy the job of repacking your rear axle bearings? Especially when the inner seal has failed? (Fromage: you read my mind)

Regarding water contamination, if you have a properly vented axle with the vent line terminated higher than any water that you might encounter, I BELIEVE you are less likely to take in water with the inner seals removed. Here is my thinking:

Water can only enter the differential via the seals (pinion or outer seals) or via the vent tube. We've already eliminated the vent tube by positioning the vent tube opening high. Assuming your outer seals are good (if they aren't, you would be seeping grease) water will only enter if there is a pressure differential. So how do you create a pressure differential? Under normal operation, the whole axle will get warm, warming the air contained within. You submerge the axle in cool water during a water crossing cooling the air contained within thereby reducing the pressure. The pressure in the main housing is equalized via the vent tube. The air in the hubs which is now at a reduced pressure is trapped between the inner and outer seals and has no way equalize except by leakage past the seals. If you are lucky, the inner seal will leak and you will only suck a little gear lube into the hub. If you are unlucky, the outer seal will leak and you will suck water into the hub.

With the inner seal removed, the hub space becomes part of the main housing space and therefore any pressure differential will be equalized via the vent tube.

 

[watrob]

I think Astr wants to change it because repacking wheel bearings sucks and because he doesn't particularly like doing it.

So how often would you redo your rear hubs, what every 7-9 years.

 

[lostmarbles]

.... What I gain is the ability to have axle shafts made more economically by not having to have the sealing surface for the inner seal on the axle shafts. They would be a large deviation from what the axle mfg's are used to making and the opportunity for error and increased cost are significant...

You're right...

My replies are made in opposition to the idea of converting grease-lubed to oil-lubed on the basis of it being an "overall improvement" and I have been overlooking what prompted you to do it in the first place.

...FWIW most of the bearing pre-load stuff-ups that I've seen (or done) have been too little pre-load. My 4x4 mentor once told me "Thom, those are big bearings. You're going to have to work to make them too tight, but too loose is easy to do and will cost you a spindle from an inner race spinning on it."

I've long pondered why Mr. T went to the added trouble of using grease. The only thing that I can find for certain is that it makes both axles the same in terms of bearing maint. and reassembly. I see no advantage, either way, in the case of water contamination.

It is interesting that my experience differs here.. In my early years of my BJ40 ownership I replaced all my wheel bearings paying particular attention to obtaining FSM bearing preload figures. After this work I did notice some of my hubs were almost too hot to touch but because I'd taken so much care to do things "right" I thought they'd be OK. (They certainly had no bearing play to worry about because the adjusting nuts had significant pressure pulling the outer and inner taper-roller bearings together.) But around 100,000kms down the track (and I could check my records for a more accuracy) I did start to get play in at least one wheel and on investigation I found signs of overheating everywhere and 2 damaged spindles/stub-axles (each showing excessive wear where the outer bearing's inner race had been spinning).

You could argue that maybe I should have repacked/reset my wheelbearings within that mileage and thus avoided the damage ... but my view of those BIG bearings is that if they're set-up correctly and packed correctly they should last almost indefinitely ... provided you haven't done any deep water crossing which I knew I hadn't.

I don't think overpacking with grease was the cause of my overheating (and they certainly weren't underpacked). Instead I think the FSM preload figures I used were excessive.

Since then I've been adjusting the nuts "to eliminate play and just a tad more" (without bothering to measure preload) and never had any further issues.

Do really enjoy the job of repacking your rear axle bearings? Especially when the inner seal has failed? (Fromage: you read my mind)

Regarding water contamination, if you have a properly vented axle with the vent line terminated higher than any water that you might encounter, I BELIEVE you are less likely to take in water with the inner seals removed. Here is my thinking:

Water can only enter the differential via the seals (pinion or outer seals) or via the vent tube. We've already eliminated the vent tube by positioning the vent tube opening high. Assuming your outer seals are good (if they aren't, you would be seeping grease) water will only enter if there is a pressure differential. So how do you create a pressure differential? Under normal operation, the whole axle will get warm, warming the air contained within. You submerge the axle in cool water during a water crossing cooling the air contained within thereby reducing the pressure. The pressure in the main housing is equalized via the vent tube. The air in the hubs which is now at a reduced pressure is trapped between the inner and outer seals and has no way equalize except by leakage past the seals. If you are lucky, the inner seal will leak and you will only suck a little gear lube into the hub. If you are unlucky, the outer seal will leak and you will suck water into the hub.

With the inner seal removed, the hub space becomes part of the main housing space and therefore any pressure differential will be equalized via the vent tube.

Having a high vent is certainly a good idea.

But water pressure will still force muddy water through seals even if the pressure inside is equalised to atmosphere (.....just at a lower rate than if there was a degree of vacuum inside).

It is these sorts of arguments (that are suggesting benefits to ALL owners resulting from changing wheelbearings to "oil-bath-lube") that prompt me to continue posting against the idea.

 

[Tapage]

The only advantage I see from the Mr. T design it's having one extra oil seal to keep diff oil out from rear brakes ..

 

[watrob]

I also have found a lot of owners who have front knuckle leaks and have contaminated front knuckles, is that they don't soak/cover the new felts on the back of the knuckles with grease before they install them. The felt's soaks up water & dirt on the first outing and another issue is if you don't grease the felt's it can effect the preload by a couple lbs loading on the knuckle when testing.

The back axle/hub is easy to pull off, re-seal & re-bearing, fronts are a pain, specially if you have to put a new rotor on, its something you only want to do every 4 or 5 years.