Birfield: Grease or Gear Lube... Birf Boot!? (2 Viewers)

[93Chewbacca]

It is my opinion that if the wiper seals in our Birfields were better at containing a less viscous lubricant inside the Birfs, that using a heavy gear oil (molybdenum fortified) would work just as well, if not substantially better than using grease. Once again, this is just my OPINION but here is why I feel this way:


I used to own a 1976 GMC 3/4 ton 2WD pickup with the Corporate 14 bolt rear axle (and a 454) (this axle is known for being brutally strong). This axle is a full floating rear axle design and the wheel bearings are lubricated by the gear oil in the axle (not grease). Gear oil would travel from the diffrential housing, through the axle tubes and into the bearings at the end of the tubes. This design worked very well and I never had ANY wheel bearing problems. My father ordered this truck from the factory and it has been in the family since new (he never had any issues either).


One of the benefits to this design (in my opinion) is that the bearings have access to MUCH more lubricant (and the lubricant circulates regularly) and thus the bearings last a VERY long time. When we pack bearings with grease, how much of the grease ACTUALLY circulates through the bearing on a regular basis? My experience is that only a small portion of the grease that we put into the bearing and the immediate area around it actually circulate through the bearing. If the corporate 14 axle design used a closed compartment design and the bearings were lubricated with grease, I think the bearing life would be much shorter.


The front Birfield design in our LC's doesnt hold gear oil well, it will leak (sometimes A LOT) because the felt gasket is not designed to hold less viscous lubricants. So it is my guess that Toyota knew that if gear oil was used in the Birf housing, the oil would leak out and many Birf joints would fail which would be a warranty nightmare (they already have enough of those). Plus, even if the failure didn't happen quickly, there would be many crabby LC owners complaining about oil leaks on their garage floors. Designing a birf that could hold gear oil would probably be difficult.


Another concept that makes me think gear oil would be better for the Birf, is centripetal force. As the Birf joint spins, centripetal force will attempt to move the grease OUT of the joint, especially the center section where the balls are. If we are instructed by the service manual to put a thick grease (NLGI 2) in the Birf housing, and this grease moves out of the KEY part of the joint, how does the grease get back INTO the joint?? If your grease maintains its viscosity, it will NOT go back into the joint easily. Gear oil on the other hand will go right back into the joint whenever the joint slows down or stops spinning. Gear oil would also be nice because it would flow out of the Birf housing and into the wheel bearings, keeping them nicely lubricated.


It is my opinion that many of our Birfield joints fail because the grease leaves the joint and doesn't get back in.


So my guess is that Toyota recommends using grease because it doesn't leak out quite as easily as gear oil would, because vehicle owners wouldn't check (and fill) the gear oil frequently enough, AND because it provides sufficient lubrication to allow the joint to last for an acceptable amount of time.


In my opinion, gear oil should be fine for the bearings and the joints (especially if the birf housing were filled to 3/4 full). I don't think grease is the best solution for the birfield joints, I think they would last longer with gear lube.


I know there are many advocates of using the specified grease and I am not saying that you are wrong to use grease (heck, I just bought 5 tubes of Amsoil synthetic moly for the Birfs) . I think grease is an excellent lubricant, I just have to wonder HOW the grease gets back into the joint after high speed rotation (I realize some greases are thick enough to resist being slung out of the joint). If there were a good way to make sure the grease didn't work its way out of the joint, everything would be perfect!


Maybe we need a Birf Boot?

 

[little_joe]

You realize that what we refer to as grease is largely a wax-like substance that suspends the actual lubricant? and that lubricant has no problem whatsoever getting into and staying on the birf surfaces? This is why our knuckles leak fluid, not wax.

Land Rover used gear oil in their front axle swivels. I owned a Rover and aside from it's general crappiness, its swivel is an inferior design - if you get a leak and don't catch it soon enough, it is a catastrophic failure. Also, squirting some grease into a knuckle that has a leak is much preferred over shooting gear oil into a leaking knuckle on a trip/4WD adventure.

Comparing a rear axle setup to the front is disengenuous, that rear axle didn't have the complications of having to steer with the associated components like a floating, pivoting knuckle.

And it's centrifugal.

 

[callum]

You realize that what we refer to as grease is largely a wax-like substance that suspends the actual lubricant? and that lubricant has no problem whatsoever getting into and staying on the birf surfaces? This is why our knuckles leak fluid, not wax.

Land Rover used gear oil in their front axle swivels. I owned a Rover and aside from it's general crappiness, its swivel is an inferior design - if you get a leak and don't catch it soon enough, it is a catastrophic failure. Also, squirting some grease into a knuckle that has a leak is much preferred over shooting gear oil into a leaking knuckle on a trip/4WD adventure.

Comparing a rear axle setup to the front is disengenuous, that rear axle didn't have the complications of having to steer with the associated components like a floating, pivoting knuckle.

And it's centrifugal.

Its only a catastrophic failure if you don't maintain it. The longevity of the components in a land rover swivel is much greater than that of the landcruiser and this is on account of it lying in a bath of oil, rather than being surrounded by grease. When land rover moved to one-shot swivel grease, the number of cv's having to be replaced due to wear went up.

I don't think its fair to say its an inferior design. The components last longer and the whole assembly can be unbolted and replaced if the wear gets too much.

Compare that to the land cruiser where people moan ad-infinitum about rebuilding the front axle and who's swivel balls look more like old canon balls because they cannot be replaced.

I run my land rover with cv boots and in 10 years, I have never even seen my swivels. Steering is smooth, wheels turns smoothly and cv's are click free. At 220000km, the contents of the hub are the same it left the factory with. In contrast, i am very familiar with the hub assembly of my landcruiser, inside and out and the o/s cv was like a maraca when i pulled it out.

 

[93Chewbacca]

You realize that what we refer to as grease is largely a wax-like substance that suspends the actual lubricant? and that lubricant has no problem whatsoever getting into and staying on the birf surfaces? This is why our knuckles leak fluid, not wax.

The knuckles leak fluid (and sometimes grease) because the seals wear out or are not designed for lubricants that are "fluid".

Land Rover used gear oil in their front axle swivels. I owned a Rover and aside from it's general crappiness, its swivel is an inferior design - if you get a leak and don't catch it soon enough, it is a catastrophic failure. Also, squirting some grease into a knuckle that has a leak is much preferred over shooting gear oil into a leaking knuckle on a trip/4WD adventure.

I would agree, IF you can actually confirm that the grease makes it into the important parts of the joint, which, IF it happens, probably does not happen right away.

Comparing a rear axle setup to the front is disengenuous, that rear axle didn't have the complications of having to steer with the associated components like a floating, pivoting knuckle.

I am not trying to pretend I know less than I do or be insincere (disingenuous), but you're EXACTLY right about the rear axle not having to contain steering components. Of course the rear axle doesn't have steering components, thats my whole point. And so Toyota designed the front Birfield joint as best they could, but what I am saying is that I wish we could use gear lube in the Birfield instead of grease. Gear lube (if contained well) could provide superior lubrication, in my opinion. I am comparing oil-bath lubrication to grease lubrication here.

And it's centrifugal.

Taken from the Isaac Newton Physics Archive at: Centripetal vs. Centrifugal Forces

When the trajectory of an object travels on a closed path about a point --
either circular or elliptical -- it does so because there is a force pulling
the object in the direction of that point. That force is defined as the
CENTRIPETAL force. It has not been more simply, or directly stated than by
one Isaac Newton in his famous "Principia" (definition 5):
"A centripetal force is that by which bodies are drawn or impelled, or any
way tend, towards a point as to a center."

This force can be demonstrated by twirling a ball on a string, and either
actually or conceptually cutting the string. The ball's trajectory is then a
straight line tangential to the closed trajectory at the instant the string
is cut. This is also illustrated by what happens to the ball in the "hammer
throw" of track and field. The athlete spins the heavy ball around several
times then lets it fly. It takes off in a straight line (not quite, because
the hammer is actually not spun parallel to the ground, but that is not
relevant).

That is really all that is necessary. The term CENRTIFUGAL force appears to
have come about because of a mistaken perception that there is a force that
operates in the opposite direction as the CENTRIPETAL force. But that is a
misconception. The "pull" that is felt by the ball on a string or by the
hammer thrower is the force that has to be applied toward the center, to
keep the ball from flying off tangentially, not radially.

Unfortunately, the terms are often used interchangably, or incorrectly.
Newton's term, which I think should take the prize is CENTRIPETAL.
(end of quote)


Honestly, in my opinion, Land Cruisers are EXCELLENT vehicles. In my opinion, the 80 series LC is one of the finest AWD vehicles on earth, BUT they are not perfect (nothing is) and they do have SOME faults. This thread is simply a statement about how I think the Birfield joint LUBRICATION could be improved.


-

 

[bhmmapping]

You just need to get some backwoods goop for the knuckles.

 

[93Chewbacca]

You just need to get some backwoods goop for the knuckles.

My opinion is that a grease that is JUST thin enough to run back into the joint while the joint is not spinning would be perfect. Ideally it would be synthetic grease with molybdenum added.

 

[Rix86]

The grease does a good job of staying in the birf.
here's an 80 during dissassembly:

Now you can kinda see how the grease is just slightly discolored, the kinda greenish tint. so it's just a tad thinner than it would be when it was new. The other side was getting almost runny, but I didn't take any pictures of the other side.
There's still grease in there, in a full time rig, driven on the freeway just about every day.
Centrifugal and centripedal force, as you're stating, aren't the only things going on in there.

 

[93Chewbacca]

The grease does a good job of staying in the birf.
here's an 80 during dissassembly:

Now you can kinda see how the grease is just slightly discolored, the kinda greenish tint. so it's just a tad thinner than it would be when it was new. The other side was getting almost runny, but I didn't take any pictures of the other side.
There's still grease in there, in a full time rig, driven on the freeway just about every day.
Centrifugal and centripedal force, as you're stating, aren't the only things going on in there.

Rix86,

That looks pretty good, thanks for the picture! I think maybe what I really need is just some real world pictures to illustrate that the grease stays where it is supposed to, so thank you

Maybe I am just thinking WAY too hard about this

 

[Rix86]

You wouldn't be the first one.
This is a non-issue that gets blown out of proportion (google tranny frank, backwoodsgoop, or ih8mush for some entertainment) for no good reason. there's been multiple topics about it, people have tried using thinner lubes, greases, heavy oils, etc, to varying degrees of disaster.

 

[bhmmapping]

Maybe I am just thinking WAY too hard about this

I think you are definitely overthinking it, but you wouldn't be the first. If you go back a few years there were several threads about this. IIRC someone packed the birfs with one color grease, added another color through the fill hole and found that the new grease moved into the birf.

 

[93Chewbacca]

You wouldn't be the first one.
This is a non-issue that gets blown out of proportion (google tranny frank, backwoodsgoop, or ih8mush for some entertainment) for no good reason. there's been multiple topics about it, people have tried using thinner lubes, greases, heavy oils, etc, to varying degrees of disaster.

I think you are definitely overthinking it, but you wouldn't be the first. If you go back a few years there were several threads about this. IIRC someone packed the birfs with one color grease, added another color through the fill hole and found that the new grease moved into the birf.

Thanks guys. I will drop the idea of using a liquid lube. I appreciate your info

 

[Kernal]

I didn't understand how everything in the front axle worked including the grease, seals, spindle bushings, birfields, etc until I pulled it all apart for the first time, cleaned and regreased everything, and put it all back together. It's a required experience if you want to learn how it all works.

 

[firetruck41]

Works fine as is, there is no solution I am aware of to use gear lube instead, so I don't concern myself about some theoretical better option.

 

[little_joe]

93Chewbacca, my apologies on the centripetal vs centrifugal comment.

You don't have to have a buildup of the wax media inside the actual joint to have lubricant in there, but of course it helps. Again this is the suspension/packaging of lubricant. Each birf I've seen, regardless of maintenance history, has had the wax & lubricant in the actual joint.

callum congrats on your Rover, you must have got the good one they built that year. I was commenting on the possibility of catastrophic failure, where a leak on a Rover swivel would be catastrophic to the joint while driving. I doubt anyone checks their swivels during every road trip. For survivability/reliability, I'll take the Cruiser knuckle any time.

As mentioned, there is a funny hysteria and overanalysis of birfs, but I guess that's part of the Cruiser OCD.

 

[Rix86]

As mentioned, there is a funny hysteria and overanalysis of birfs, but I guess that's part of the Cruiser OCD.

trannyfranksayswhat?