Why have an inner seal on FF? (1 Viewer)

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I can state, without reserve, that removing the seals and using oil to lubricate the rear axle bearings has worked for me for the last 3 years at least.
 
cat-pushing-watermelon-out-lake-invalid-argument.jpg
 
If you're tired of the discussion then why are you paying it any attention?

I really do think that the little seal and grease in the bearings is one of the few times that Mr. T has overly complicated something when the rest of the world does just fine with oil. Their seals don't leak any more or less than usual, their brake backing plates are designed like Mr. T's, to deal with the occasional leak and attempt to direct it away from the brake linings. It's well proven and works for every other FF mfg that I'm aware of over trillions of miles. Statistically grease & seals is the unproven option in comparison to oil and no seal, but both set of miles driven w/o problem are so large that the whole point is moot.

If you want to keep the seals and run grease then go for it, I'm not going to care or attempt to "convert" you to the dark side. It certainly works, but don't try to trivialize my point of view with stupid pictures.
 
I posted on this thread years ago. I can't believe it's still alive.

Anyway, to add something useful:
My HJ60 is a FF, and the part number for the seal is 90310-35001.
A reverse lookup shows it was in use from 1969 till 2006.
Including the Dyna, which may indicate it is not necessarily an off-roading consideration.

If the seal is not that necessary, then Toyota have been using it for no reason, for a very long time.
 
It is necessary IF you use grease. It is undesirable if you use oil.
 
.... but don't try to trivialize my point of view with stupid pictures.

And I thought that pic was aimed at me :D
 
THIS IS WHY WE CAN"T HAVE NICE THINGS!!!

Am I too late? I'd hate to steal someone else's thunder.
 
Yes... Oil will lube the seal lips better. (Damn ... a point conceded :D)

But as for the breather argument, diffs have far greater need for a breather because there is so much more trapped-air inside.

And no matter whether your hubs are vented (to some safe level) or not, if you submerge them you are always likely to get water ingress because the pressure differential from depth-of-water is the main driving force.

So I suspect "hub water ingress rates" would vary very little between "vented" and "sealed" setups.

:beer:

(Who's going to run out of breath first in this? ......................:))

The pressure difference from submersion is one factor and a relatively constant one. A foot down you'll have about half a psi. That's pretty minor.
What does make the difference is whether the inside of the hub cavity is at ambient pressure (0psi) or pulling a vacuum (-5psi wouldn't be impossible).

And think how travelling on steep side-cambers will tend to fill the hub on one side while draining the other one ...

My rangie hubs take maybe 200cc each max. But draining them takes forever. On a side-slope you can't get much oil out the high side (the protruding stub is the only exit and it gets higher the more you lean over) and the low side has an air-lock preventing it completely filling.

When you take an oil hub off, they'll drip into a try for days. All those cavities in roller bearings are great at holding oil. Accidentally running them dry isn't a concern I've ever had.
 
The pressure difference from submersion is one factor and a relatively constant one. A foot down you'll have about half a psi. That's pretty minor.
What does make the difference is whether the inside of the hub cavity is at ambient pressure (0psi) or pulling a vacuum (-5psi wouldn't be impossible).....

When a warm hub gets immersed in cold water the metal housing actually contracts in size as it get cooled which by itself would actually tend to compress the air trapped inside. (True that this is effect is pretty negligible, but your -5psi figure above is just "plucked from the air" so it deserves an equally-dodgy counter argument Dougal. :D)

But there is more to my armoury..

To get the "vacuum" you talk of, the trapped air must be cooled and this process of transferring heat from the air to the cold hub metal takes much more time than the transfer of heat from the hub-metal to the water. So a short water crossing is unlikely to produce anything measurable as far as vacuum goes (in a grease-lubed hub)... whereas someone getting stuck in a boghole or during a river crossing is a completely different story.

And let's look at that more deeply. (Excuse the pun.)

So when someone has been stuck for 10 minutes in the middle of a river do you still think temperature difference would be having the major effect?

At that point, the trapped-air temperature won't be far off the river temperature!

In this scenario the absence of any vent tubing (to vent an OEM grease-filled hub) gives it the advantage that for more water to enter, an equal volume of air needs to escape past the seals. In other words, the lack of a vent tube is actually restricting the rate of further water ingress here.

...My rangie hubs take maybe 200cc each max. But draining them takes forever. On a side-slope you can't get much oil out the high side (the protruding stub is the only exit and it gets higher the more you lean over) and the low side has an air-lock preventing it completely filling.

When you take an oil hub off, they'll drip into a try for days. All those cavities in roller bearings are great at holding oil. Accidentally running them dry isn't a concern I've ever had.

You're right on this point. (I was tongue-in-cheek with that bit ....or else I got carried away and lost my mind temporarily - Take your pick.)..If someone did do a "oil-lubed-hubs conversion" on a 40-series and managed to get oil into both hubs, then I admit it would be very hard for any hub to run dry again. (But I still do agree with Watrob that the fill-plug position would need to be raised on the 40-series LC diff housing for such a conversion to be sound.)

And one final point (because hopefully I'll resist any further additions to this thread) ... Early 40-series cruisers have their handbrake shoes located right next to their rear-drive output oil-seals on the transfer cases. Surely no-one can argue that the performance of these brakes are seldom harmed by oil leaks?

My handbrake (designed like this) normally performs admirably but I am always aware that when I need it most (such as on extremely steep bit of track when I've lost traction and found I'm really in the sh#t ) some oil will inevitably tip off a seal lip (or wherever) onto the linings and make it barely hold (even when the braking action of the shoes are being backed up by having the transmission in low-ratio 1st and I've turned my engine off to get out and pull my hair out).

So I still thank Mr Toyota for making sure none of my other brake linings are so close to oil seals!

:beer:
 
When a warm hub gets immersed in cold water the metal housing actually contracts in size as it get cooled which by itself would actually tend to compress the air trapped inside. (True that this is effect is pretty negligible, but your -5psi figure above is just "plucked from the air" so it deserves an equally-dodgy counter argument Dougal. :D)

Yeah fair enough, lets calculate it then.
We all know PV=mRT.
Rearranges to P=mRT/V.
If we are holding volume, number of molecules constant then the only variable is temp.
This comes down to change in P is proportional to absolute change in T.

Take an axle running at 50C (323K) and put it into water at 10C (283K).
The change in pressure will be the ratio of 283/323 = 0.876.
If we started with 101.3kPa or 14.7psi (atmospheric) then we'll now have 88.7kPa or 12.8psi.

A bit under 2psi vacuum from a change in temp of 40C.

But there is more to my armoury..

To get the "vacuum" you talk of, the trapped air must be cooled and this process of transferring heat from the air to the cold hub metal takes much more time than the transfer of heat from the hub-metal to the water. So a short water crossing is unlikely to produce anything measurable as far as vacuum goes (in a grease-lubed hub)... whereas someone getting stuck in a boghole or during a river crossing is a completely different story.

And let's look at that more deeply. (Excuse the pun.)

So when someone has been stuck for 10 minutes in the middle of a river do you still think temperature difference would be having the major effect?

At that point, the trapped-air temperature won't be far off the river temperature!

In this scenario the absence of any vent tubing (to vent an OEM grease-filled hub) gives it the advantage that for more water to enter, an equal volume of air needs to escape past the seals. In other words, the lack of a vent tube is actually restricting the rate of further water ingress here.

The volume of air inside a hub will reach the metal temp within seconds. Any river crossing I've done takes at least 10 seconds and will do that. You've then pulled the vacuum above and unless your seals can sustain the 2psi then you'll bring in water through the seals to minimise the vacuum.

Venting the hubs above the water line will remove the vacuum and prevent the problem. Oil bathing the hubs connects them to the main axle breather which also prevents the problem.

And one final point (because hopefully I'll resist any further additions to this thread) ... Early 40-series cruisers have their handbrake shoes located right next to their rear-drive output oil-seals on the transfer cases. Surely no-one can argue that the performance of these brakes are seldom harmed by oil leaks?

My handbrake (designed like this) normally performs admirably but I am always aware that when I need it most (such as on extremely steep bit of track when I've lost traction and found I'm really in the sh#t ) some oil will inevitably tip off a seal lip (or wherever) onto the linings and make it barely hold (even when the braking action of the shoes are being backed up by having the transmission in low-ratio 1st and I've turned my engine off to get out and pull my hair out).

So I still thank Mr Toyota for making sure none of my other brake linings are so close to oil seals!

:beer:

Landrover does the TC mounted drum-brake hand-brake too. They have an oil catcher inside so when your rear TC oil seal leaks it is drained out and can be seen dripping off the backing plate behind.
I did mention earlier I've had oil soaked brakes before. The vehicle still stops, braking capacity is reduced by a bit under half (only one brake gets wet) and the vehicle pulls under braking.
It's not the immediate certain death that many assume it'll be.

Another good example just came to mind. All tractors run oil bath wheel bearings and until the last few decades they also ran drum brakes. Axle seals failures are common, but they almost never cause brake problems.
 
OK Couldn't resist one more post ...


Ahhh.mmmm (Clearing throat....)

Yeah fair enough, lets calculate it then.
We all know PV=mRT.
Rearranges to P=mRT/V.
If we are holding volume, number of molecules constant then the only variable is temp.
This comes down to change in P is proportional to absolute change in T.

Take an axle running at 50C (323K) and put it into water at 10C (283K).
The change in pressure will be the ratio of 283/323 = 0.876.
If we started with 101.3kPa or 14.7psi (atmospheric) then we'll now have 88.7kPa or 12.8psi.

A bit under 2psi vacuum from a change in temp of 40C...

So with ideal-situation maths, hot-to-touch hubs, and pretty-cold water you now calculate a value less than half of your earlier "wouldn't-be-impossible figure" of 5psi Dougal!

...The volume of air inside a hub will reach the metal temp within seconds. ...

Heat exchanger manufacturers go to a lot of trouble to extend surface area when trying to carry heat to/from air. Yet you say a smooth hub surface covered in grease achieves such a great result? That's truly amazing!

.. Any river crossing I've done takes at least 10 seconds and will do that. You've then pulled the vacuum above and unless your seals can sustain the 2psi then you'll bring in water through the seals to minimise the vacuum.

Venting the hubs above the water line will remove the vacuum and prevent the problem. Oil bathing the hubs connects them to the main axle breather which also prevents the problem....

Hubs represent a small volume. So it stands to reason that pressure difference caused by temperature change can be eliminated by similarly small volume changes. And taking this further ...If a degree of vacuum starts to develop, it probably gets reduced or even eliminated just from the flexing of the seal rubber. And when you have a double-lipped seal (as we have) any vacuum will tend to make the outer lip "pull-in" to create an even better seal to stop water ingress.

...Landrover does the TC mounted drum-brake hand-brake too. They have an oil catcher inside so when your rear TC oil seal leaks it is drained out and can be seen dripping off the backing plate behind.
I did mention earlier I've had oil soaked brakes before. The vehicle still stops, braking capacity is reduced by a bit under half (only one brake gets wet) and the vehicle pulls under braking.
It's not the immediate certain death that many assume it'll be.....

Whatever Landrover did, Toyota did better... (for similar vintage)

Wayne? Are you out there? Am I doing alright? (I'm wasting too much time here... so I need someone else to take over..)

:beer:
 
OK Couldn't resist one more post ...

Ahhh.mmmm (Clearing throat....)

So with ideal-situation maths, hot-to-touch hubs, and pretty-cold water you now calculate a value less than half of your earlier "wouldn't-be-impossible figure" of 5psi Dougal

Get them hot enough and you can pull whatever vacuum you want.

Heat exchanger manufacturers go to a lot of trouble to extend surface area when trying to carry heat to/from air. Yet you say a smooth hub surface covered in grease achieves such a great result? That's truly amazing!

Indeed, but heat exchanger manufacturers are trying to continually shift many kilowatts of heat so they continually chase max heat transfer. This case we only need to cool the case, the heat storage in the air inside is so small in comparison that it's essentially tied to the case temperature.

Feel free to conduct some experiments with baked bean cans, greased up inside with balloons stretched over the top to see and show.

Hubs represent a small volume. So it stands to reason that pressure difference caused by temperature change can be eliminated by similarly small volume changes. And taking this further ...If a degree of vacuum starts to develop, it probably gets reduced or even eliminated just from the flexing of the seal rubber. And when you have a double-lipped seal (as we have) any vacuum will tend to make the outer lip "pull-in" to create an even better seal to stop water ingress.

Well this is the interesting thing. The hubs clearly aren't anywhere near perfectly sealed or they would always be slightly pressurised or vacuumed. Even weather conditions cause a pressure change and somehow the hubs are breathing air in/out to equalise.

Submerge them in water and it's not air they're breathing in/out anymore, any suck in is going to bring water with it.

Whatever Landrover did, Toyota did better... (for similar vintage)

10-20 years later if/when they got around to copying them. They took 20 years to follow the rangerover with coil springs and disc brakes, were 40 years behind putting a V8 in a 4wd. Still haven't got air suspension and I haven't heard much about off-road traction control either.

But that's getting back to the whole lead vs follow thing.

Wayne? Are you out there? Am I doing alright? (I'm wasting too much time here... so I need someone else to take over..)

:beer:

Yeah I need to get some more work done too.[/QUOTE]
 

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