Why have an inner seal on FF?

[Dougal]

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...

Sure a wheel bearing set will last a lifetime with grease if kept dry, kept cool and initially setup correctly. But how many bearings do?

My rangie came from the factory with oil lubed wheel bearings, it had done about half a million km (odo said 350,000km but the dealer who imported and sold it at 100,000km was shut-down for winding back cars). In that time I replaced two front hub bearings due to wear and had one oil seal failure which may or may not have been my fault (hub installation).
The axles I replaced them with had ~80,000km on them, were greased from the factory and already showed signs of both being hot and having been re-adjusted. Not sure which came first, the readjustment or the burning, but oil bath bearings can't get hot enough to scorch blue.

I converted those axles to oil. I had one issue with a front seal that kept weeping. I had to re-machine a stub-axle seal seat to get a seal. It's been perfect since.
But this was on an axle which does have bolt on/off stub axles. If your stubs are welded on then you're kinda screwed.

The benefits of oil bath are better lubrication, better cooling, longer bearing life and better exclusion of contaminants. It is also much easier to drain and flush than trying to wash out water contaminated grease.

Grease is much, much cheaper for the manufacturer than an oil bath. Both in parts, assembly and warranty. In my experience Toyota is the manufacturer who shies away from anything except tried and true.

 

[Douglas S]

Grease is much, much cheaper for the manufacturer than an oil bath. Both in parts, assembly and warranty. In my experience Toyota is the manufacturer who shies away from anything except tried and true.

I'm with you right up to here.

There are fewer parts with an oil bath (no inner seal, no extra machined seal surface on axle shaft) and assembly is easier/faster because no inner seal needs to be installed and the bearings do not need to be packed with grease. How do you figure greased bearings to be less expensive?

 

[lostmarbles]

.... If your stubs are welded on then you're kinda screwed...

Hi there Dougal.

On a 40-series our rear "stub-axles" are part of the diff-casing (and so are equivalent to your description of "welded-on") whereas our fronts are separate bolted-on components (and are thus easily replaceable).

So with a 40-series we want to particularly avoid stub-axle wear on our rear full-floaters...

...The benefits of oil bath are better lubrication, better cooling, longer bearing life and better exclusion of contaminants. It is also much easier to drain and flush than trying to wash out water contaminated grease.

Grease is much, much cheaper for the manufacturer than an oil bath. Both in parts, assembly and warranty. In my experience Toyota is the manufacturer who shies away from anything except tried and true.

Mostly I agree but "better exclusion of contaminants" and "cheaper to manufacture" and "Toyota shies away from tried and true" (especially when Toyota were the first big automotive manufacturer to put hybrid technology into mass production with their Prius model) - are all things that are very debatable.


And you don't mention the fact that these particular bearings (ie. wheelbearings) have brake-linings/pads in close proximity .... which is a "game changer" for some of us..

 

[Dougal]

I'm with you right up to here.

There are fewer parts with an oil bath (no inner seal, no extra machined seal surface on axle shaft) and assembly is easier/faster because no inner seal needs to be installed and the bearings do not need to be packed with grease. How do you figure greased bearings to be less expensive?

The actual cost of the oil vs the grease would be about the same. The savings are in the ancillary seals (dust seals vs oil seals) and the labour of installation on a production line.

Hi there Dougal.

On a 40-series our rear "stub-axles" are part of the diff-casing (and so are equivalent to your description of "welded-on") whereas our fronts are separate bolted-on components (and are thus easily replaceable).

So with a 40-series we want to particularly avoid stub-axle wear on our rear full-floaters...



Mostly I agree but "better exclusion of contaminants" and "cheaper to manufacture" and "Toyota shies away from tried and true" (especially when Toyota were the first big automotive manufacturer to put hybrid technology into mass production with their Prius model) - are all things that are very debatable.


And you don't mention the fact that these particular bearings (ie. wheelbearings) have brake-linings/pads in close proximity .... which is a "game changer" for some of us..

The prius is indeed an outlier for Toyota. Everything else they do is more evolution than revolution. This is I believe a large part of their appeal. Buyers looking for improvement of the previous vehicle etc.

Most of us have brakes near hubs. The Brits accepted that anything with oil in it would leak and put in catcher plates and drains. I haven't been in a toyota hub to compare. But if they were greased then there would be no reason for these. I have had seal failures spit oil over my (disc) brakes. It only gets one side which is a slight improvement. A squirt of brake-clean then drive them hot (same as bedding in new pads) and they're good again when the smoke clears (not joking).

I do recall you telling me of the front gearbox seal that dumped oil straight into your clutch!

The exclusion of contaminants is more about the seals. To seal oil in requires a better seal than to keep dust out of grease. This can be a major problem if you're left sitting in water or mud over the hubs. All the heavy machinery I've dealt with ran oil bathed hubs. Even track chains in larger diggers and dozers have each pin sealed and run in oil.

Of course if grease is working fine for you and where/how you drive, why would you bother to change?

 

[lostmarbles]

.....I do recall you telling me of the front gearbox seal that dumped oil straight into your clutch!...

Yep. And this supports both of our arguments:

• It supports mine in that it shows oil seals can readily "let go for no apparent reason" to spew oil over friction lining/pads (because the original seal failed at about 40,000kms and my replacement seal is still going well over 200,000 later) and
• It supports yours in that it shows Toyota does indeed place oil seals next to friction-pads

However a slipping clutch is not usually a serious safety issue whereas oil on brake linings/pads always is.

....The exclusion of contaminants is more about the seals. To seal oil in requires a better seal than to keep dust out of grease. ......

When I look at the grease seals we have on our Land Cruiser hubs (ie. - those big one's that are pressed into the back of our hubs after the inner bearing is installed) ...... they look no inferior to any oil seals I've seen as far as their sealing ability. In fact they're double-lipped!

Not only this, but when you slide each hub onto its "stub-axle" the end of the hub itself enters a completely separate seal (located in the brake backing plate). Now this seal IS one that could indeed be described as "merely a dust seal". But it is separate from the main seal and doesn't just stop dust. It serves also to reduce the likelyhood of grease (that has somehow made it past the double-lipped seal) getting on your brake linings.

So Toyota went to all this trouble just to keep wheelbearing-grease away from brake linings!

And oil is far more likely to escape through seals than grease is.

 

[ntsqd]

Oil is also far more likely than grease to keep the seal's lip wetted and therefore both lubricated and cooled.

 

[Dougal]

So how does a typical Toyota grease lubricated hub breathe for temperature changes?

With oil bath, expansion/contraction (worst example is a hot hub driven into cold water) is handled by the axle breather. So when they cool and the air inside contracts the air needed is pulled through the breather.
If a grease hub has no breather, does it pull air through the seals in such a situation? If the hub is submerged, then it can only pull in water!

 

[watrob]

My current 40 has been in the harshest condition you could be in, 7 years full time on the beach, its garage on the beach. The rear brake rotors because they are steel, rusted because the vehicle is driven only on weekends, which in turn rips the pad material apart very quickly. But the rear hubs do not leak, I also pulled the rear diff out 2 years ago and put in a rear Lokka and the diff oil was still clean (my rear diff breather has an extension hose on it). Also this chassis has no large backing plates covering the disc rotors on the rear, not like the front axles disc brakes have.

I need to keep my hubs dry, any sign of grease or oil coming out of a seal contamination sets in very quickly.

 

[lostmarbles]

Oil is also far more likely than grease to keep the seal's lip wetted and therefore both lubricated and cooled.

So how does a typical Toyota grease lubricated hub breathe for temperature changes?

With oil bath, expansion/contraction (worst example is a hot hub driven into cold water) is handled by the axle breather. So when they cool and the air inside contracts the air needed is pulled through the breather.
If a grease hub has no breather, does it pull air through the seals in such a situation? If the hub is submerged, then it can only pull in water!

Yes... Oil will lube the seal lips better. (Damn ... a point conceded )

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.



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

 

[watrob]

Ok can I ask a question, so how much do you have to overfill a 40 series rear diff for the diff oil to lube the hub bearings (which you have removed the inner axle shaft oil seal from) to the degree they are in a oil bath? isn't that a lot of diff oil because to make sure the hub bearing were oiled you would have to fill way above the fill bung on the diff as the Toyota diff is not designed for what you are trying to do?

 

[lostmarbles]

Ok can I ask a question, so how much do you have to overfill a 40 series rear diff for the diff oil to lube the hub bearings (which you have removed the inner axle shaft oil seal from) to the degree they are in a oil bath? isn't that a lot of diff oil because to make sure the hub bearing were oiled you would have to fill way above the fill bung on the diff as the Toyota diff is not designed for what you are trying to do?

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

 

[watrob]

Yes, but further still you would have then to top up the diff as the hubs absorbs the oil, so you need an extra pint of oil in the diff. So what happens on DD's that never gets off-road. A 100klm trip on bitumen, mid summer, low diff oil, ( because if you don't over fill the diff with oil it runs back into the diff as it find its level, high temps, the bearings would not be in a bath of oil but starved of oil.

If the Toyota rear axle was designed to have the hubs run on diff oil it would have been designed that way, the diff bung would be higher in the diff so oil would get to hubs, there would then be no axle oil seals and no baffel's in the axle housing, which are all there to prevent oil from getting to the hubs to begin with.

Am not say oil bath rear hub bearings are no good, it's just the axle housing has to be designed to have this system to begin with?

.

 

[ntsqd]

Oil fill level is the same as the filler is above the level of the bottom of the housing tube. At least it is on mine. The bottom of the bearings is below the stub spindle's bore, so oil can't drain out of the of the uphill hub on a side-slope. Not even when that slope plants you on your side. Find a cross-sectional drawing, you'll see what I'm talking about.

The main mechanism that drives water into the diff housing when submerged isn't a pressure differential. That differential is too small to be the main engine driving the water contamination. What is a strong enough engine is the thermal differential. The HOT diff suddenly plunged into the COLD water is enough to draw in water because the rapidly cooled housing will have a mild vacuum in it due to the rapidly condensed air inside. Which points to the breather. The better it can do it's job the lower that vacuum will be and the less likely it will be to draw in water past the seals.

 

[lostmarbles]

Well I'm still going here (despite the fact that we're all guilty of stretching things in our arguments now)...

What you've just said about the main driving mechanism being temperature difference rather than pressure difference is nonsense ntsqd. Both "cooling action" (from a warm hub being immersed in cold water) and "depth of water" tend to force muddy water into our hubs by the same means. That is, by creating a "pressure differential". (A vacuum is still a pressure and you can measure it on a compound pressure gauge that is callibrated with units of vacuum .... or on one that reads in absolute pressure units.)

Now... Back on the subject of the oil ....I do admit that once oil gets tipped into a hub (from driving on a side-camber or going around a bend fast) sufficient oil should stay there for all lubrication/sealing/cooling purposes provided the Land Cruiser is operated normally (with a mixture of onroad and occasional-offroad driving at various speeds and on various cambers).

But you guys have had me crawling down on my hands and knees a few minutes ago looking at my rear diff out in the rain and cold so this is getting real serious.

And despite what you say about your pretty cross-sectional drawing ntsqd, the lower edge of my fill/level plug doesn't look high enough to me for the correct oil level to automatically spill oil into the hubs on level ground during the initial filling operation.

So I think Watrob is correct in that it would not be a straightforward matter to ensure that a rear axle assembly that's been freshly converted to being grease-free gets proper oil lubrication everywhere, from the word go, simply from a normal diff-housing oil-filling operation.

Think about that poor Land Cruiser owner living somewhere in this world of ours on the slopes of a volcano where tradition dictates clockwise driving (or anticlockwise for that matter) on all tracks that circumnavigate this land-pimple that he/she calls home. They may get this "brilliant oil-bath conversion idea" off ih8mud and, low and behold, they find they've been running their uphill-orientated hub dry of oil and it gets badly damaged? Could you proponents of the oil-bath-conversion-idea sleep at night knowing you caused this????

 

[roscoFJ73]

Beyond caring

 

[lostmarbles]

Beyond caring

Shame on you....

 

[astr]

I have a ford van with a Quigley 4x4 conversion, essentially a Dana 60 stuck up front. Two or three times I submerged the axles in Lake Superior (cold) after driving a bunch of trails. Upon return home I drain both front and rear axles to check for water contamination. Every time, the front axle was contaminated with water. The rear was fine. AHA! must be a blocked breather on the front. I searched and searched for the breather tube but couldn't find it so I called Quigley. Well according to them, you don't need one on the front cause you seldom use the front axle. RIGHT! I drilled and tapped the front axle housing and added a breather. Two times since the mod that I have submerged the axles and drained the lube, there was no contamination on either axle. So good venting appears to make a difference.

Ok can I ask a question, so how much do you have to overfill a 40 series rear diff for the diff oil to lube the hub bearings (which you have removed the inner axle shaft oil seal from) to the degree they are in a oil bath? isn't that a lot of diff oil because to make sure the hub bearing were oiled you would have to fill way above the fill bung on the diff as the Toyota diff is not designed for what you are trying to do?

On the 80 series filling to the fill plug will get plenty of lube to the bearings. In fact, if you want to pull an axle, make sure that the side that you are working on is raised above level or you'll end up with gear lube coming out of the end of the tube. Even with the side raised, you will still leak a couple of ounces that are trapped in the hub because of the cross section like ntsqd said.

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

Regardless of the volume of air that you are dealing with (hub or axle housing), the change in pressure due to change in temperature will be exactly the same assuming the temperature change is the same. Simple physics.

 

[ntsqd]

Well I'm still going here (despite the fact that we're all guilty of stretching things in our arguments now)...

What you've just said about the main driving mechanism being temperature difference rather than pressure difference is nonsense ntsqd. Both "cooling action" (from a warm hub being immersed in cold water) and "depth of water" tend to force muddy water into our hubs by the same means. That is, by creating a "pressure differential". (A vacuum is still a pressure and you can measure it on a compound pressure gauge that is callibrated with units of vacuum .... or on one that reads in absolute pressure units.)

Never that they weren't the same thing. I said that the depth is not the main driver and the rapid cooling is. By the time that you get the diff deep enough for the pressure head to equal what can easily be achieved with rapid temperature change it won't matter because you're also breathing water.

And despite what you say about your pretty cross-sectional drawing ntsqd, the lower edge of my fill/level plug doesn't look high enough to me for the correct oil level to automatically spill oil into the hubs on level ground during the initial filling operation.

So I think Watrob is correct in that it would not be a straightforward matter to ensure that a rear axle assembly that's been freshly converted to being grease-free gets proper oil lubrication everywhere, from the word go, simply from a normal diff-housing oil-filling operation.

I said mine was high enough. I've no knowledge or info about any others. This was one of the first things that I checked in considering this option.

Think about that poor Land Cruiser owner living somewhere in this world of ours on the slopes of a volcano where tradition dictates clockwise driving (or anticlockwise for that matter) on all tracks that circumnavigate this land-pimple that he/she calls home. They may get this "brilliant oil-bath conversion idea" off ih8mud and, low and behold, they find they've been running their uphill-orientated hub dry of oil and it gets badly damaged? Could you proponents of the oil-bath-conversion-idea sleep at night knowing you caused this????

Yep. If they can't think things like this thru for themselves they shouldn't be veering away from what the FSM calls for.

 

[maat]

so after reading a six page thread on seals I've learnt:

lost marbles has a pretty big hard on for crushers,

removing these seals *could* be bad but no one really knows for sure,


theres 20 minutes of my life I will never get back.

 

[lostmarbles]

I'm truly sorry for taking 20 minutes of your life Maat. That's probably equivalent to 40 stolen minutes elsewhere too because we must remember that you're in "a state of excitement"..

Oops. Just checked, Western Austraaaalia keeps changing. After "the state of excitement" you became "the golden state" and now you're apparently "the real thing".

Must've ceased to be a state of excitement after I left in 1981. That stands to reason.

Well ... Taking 20 minutes of time away from someone who's engaged in "the real thing" is bad too I guess. So I AM truly sorry...

PS. And we do need Wayne to join this thread. I think that's what's missing on ih8mud now. If he was his usual self (and not sulking away upset at the new forum layout) we could have relied on him to slug it out with Dougal for a few more pages yet.