NP 229 - Does it have a Differential or Not

[Chevelleguy]

Well, I guess my brain was fuzzier than yours Ristow. RISTOW WAS RIGHT, AGAIN!!!

I don't remember seeing that part when I had mine apart. See how the side gears engage the clutch plates? It has to have the friction of the silicone fluid and the shear plates to transfer power. When all the fluid leaks out, you will have slippage or , if it is burnt real good, no forward movement in 4hi. That is why I tore into mine, it made a mechanical whine and had slippage, reduced forward motion, in 4hi.

I have had to go into one that wouldn't hold park and had no movement in 4hi. Replace with a good used coupling and it was fixed. Mine, I just pinned the coupling so now there is no differential action.

[Chevelleguy]

Wonder what would happen if you welded that up?
(just wondering, don't actually own one)

No need to, you can just pin the plates in the coupling.

Mike, go ahead and pop the cover off the coupling so everyone can see the shear plates inside. Please.

[Ristow]

i have a very persistent,fuzzy brain......LOL!

[chef]

well,my fuzzy brain was insisting it remembered digging those rollers out of the differential in the VC.

so i did the only thing i could think of to be sure. i opened up an old 229 i had laying around.

the VC.



and upon removal we see.....









if that aint' a differential......you can slap me silly and call me Shirley.

You are definitely not Shirley, you are a good man for actually proving your point.

[Ristow]

Mike, go ahead and pop the cover off the coupling so everyone can see the shear plates inside. Please.

no pressure or spring in there to surprise me?

[Chevelleguy]

No, if you take the little allen plug out, you can shoot some air in it to help pop the cover off (like pushing out a brake caliper piston).

[JeepsnCellos]

Ristow saved my life!

...Or at least my job (I spent most of today looking for this answer on the web instead of working)

Thank you for doing that Ristow. This was driving me nuts. Most of the explanations of what this thing does just don't make sense given how are rigs behave. Now that I know there are spider gears in there, all is right with the world.

So the part that most call the viscous coupling is actually a full fledged limited-slip differential that utilizes a VC to limit the motion between the 2 outputs.

I can sleep tonight!

[Chevelleguy]

The problem with that theory is that when the coupling goes south, you don't get a simple open diff, you get no movement.

[Ristow]

my belief is that it's the center diff that fails on these,taking the VC out with it. which would explain the loss of motion,park,etc...

simple little device actually. cover open.



the thin metal discs.





they're in a thick gooey fluid. like rubber cement.

[Chevelleguy]

Thanks Mike. Line the holes up that are 180* apart and slip some pins in them, put it back together and you now have a part time only case.

[JeepsnCellos]

Sigh...I'm probably one of the 934+ people that are now confused beyond redemption. Let's try to get this answered for idiots like me with a simple question that hopefully addresses end results that matter to the driver.

With a 229 and no other mods:

1) When I'm running up or down a slippery road in 4WD High, whether its due to rain, mud, sand, snow, or ice, am I correct in that I can rely on at least one tire in the front and one tire in the rear will always have power to it? Yes/No?

I say "one tire" front or rear because we also have the front and rear differentials doing their thing too. And in this case we really have "2WD" because we're not locked. Yes/No?

2) But wait: If one has Limited Slip Differential in the rear (which I do), then I really have 3WD because both the rears will provide drive, but only one in the front will provide drive. Yes/No?

Rich88 - Unfortunately the answers to your questions are not as simple as you indicate.

It is a mistake to think that an open differential delivers power (or torque) to only one output. In fact, an open differential is a torque balancing device and is incapable of delivering more torque to one output (wheel) than the other. An open differential gives you exactly the same amount of torque in both wheels on any given axle. That is why if you have low traction in one wheel (and can therefore generate very little torque in that wheel) the other wheel will also have also have very little torque and will not pull your rig.

A limited slip is a torque biasing device. It allows you to develop more torque in one axle than the other. It does this by taking advantage of the differential motion between the two wheels typically using some sort of friction device.

So if you have a center differential, and 2 differentials in your axles and they are all open, you will ALWAYS have exactly the same amount of torque at all 4 wheels. I know it seems like that would be a good thing, but just think about what happens when only one of your wheels has low traction, or more dramatically, has zero traction. The torque generated in that wheel (which will be zero) is the same as sent to the other wheels. Bad news.

[JeepsnCellos]

Ristow - It would be interesting if you could collect some of that fluid and try to heat it a little. I'm curious to see if really does get thicker.

[Rich88]

Rich88 - Unfortunately the answers to your questions are not as simple as you indicate.

I'm not smart enough to discuss the matter from an engineering point of view.

I guess I could get the practical and simple answer using some bottle jacks under axles and experimenting to find out when the jacked up wheel turns vs. rocking the vehicle off the jack. Lifting one or more wheels at a time would be the ultimate slip condition.

[Tripwire]

Why are the VC's unobtainable/ un rebuildable? did they not make so many 229's or do they just eat them up due to poor engineering?

[serehill]

Sometimes

This is a great spectator sport,