Tutorial: removing the viscous coupler (photos)

[Ebag333]

I'm guessing the Toyota put it in there so that people wouldn't have to know when to push the CDL button. They made it automatic because most of the people who bought FZJ80 didn't want to know that much about how they work.

There's also some thinking that it was added to help eliminate some of the drive train slop that was found in the 91's and 92's.

So the bottom line is they aren't necessary and their function can be duplicated by the CDL switch.

While I don't think there's anything wrong with pulling the VC, it's function can't exactly be duplicated by the CDL switch. (That's why it's found side-by-side with the CDL.)

It's the equivalent of LSD rear axle vs locked rear axle. You get different behavior.

With CDL or axle locker, you get either fully opened or fully locked, basically digital (0 or 1). With VC or LSD, it's analog. You get fully opened to fully locked and everything in between.

The ability of the VC (or an LSD) to adjust on the fly is excellent in slick conditions. For the rest of the time, a locker works just fine.

 

[crooozer]

Wow, confusing stuff indeed..!

I still can't get my head around, but FWIW, The Aussie cruisers have a rear LSD. If that makes any difference

 

[Pin_Head]

It isn't that complicated. Both the VC and the CDL limit one wheel slipping by sending torque to the other axle. The VC does it automatically with no user intervention, while the CDL is a selectable on/off mechanical coupling. As long as all wheels have traction, you don't need either the VC or CDL to be eengaged.

 

[crooozer]

Ummm. Ok After 3 hours of hard work and new oil/gasket I went to fire er up with one driveshaft connected like before and NOTHING..It won't drive reverse, or forward.

Why? I've noticed when installing the rear driveshaft that the transfer case just spins continuosly in both directins, unlike before when it was in P would only spin so far and that would be it.

Whats gone wrong!!? PLEASE, I need real time help here

Place the auto trans in Reverse and I get out and look at the driveshaft, there is no spin. Did I not align the actual transfer case cover and shaft back on properly or something? It seemed like it was on right? Is this VC removal a load of crap? I'm really at a loss here.

 

[Pin_Head]

If you removed the VC and one of the driveshafts, then you need to lock the CDL in order for it to move.

If you removed the VC and both of the drive shafts are connected, then it should drive normally.

 

[crooozer]

Thanks Pin, but I don't see how it would drive with both shafts connected, not just one. None of them even spun.

I'm removing it and replacing the broken VC now and taking it down to the car lot. Thats it for me..

 

[Pin_Head]

If only one drive shaft is connected, the flange for the removed one will just spin until the CDL is locked.

Removing a drive shaft is just like having a wheel lose traction and spin.

you have to lock the center differential if you only have one drive shaft.

 

[crooozer]

Pin, thank you very much.

After I cracked it this morning I went back to the truck and disconnected both shafts, then placed the trans is reverse and both ends started spinning..!

Hooked them both up, refilled the trans case (after draining it twice..) and she goes great! My CDL seems to work just as it did before.

Thanks again mate, I'm not sure what I would have done without your help, Probably re-install the busted VC and sell the truck because it has been a real money pit as of late, but I'm thinking this might be it for a while.

 

[Pin_Head]

Carlton draught

No worries mate. You need to read up on how differentials work, especially the center diff in the transfer case. You also need to install a manual center diff lock switch in your '97 because the way they come stock, the center diff will only lock in low range.

 

[silverhorse]

Good info guys! I'll be installing my part time kit soon so i need to get familiar with the system and it's workings.....

 

[Pin_Head]

Here is a link to the operation of the differentials in a cruiser:

Welcome to Land Cruiser Owners On Line

 

[crooozer]

Thanks mate.

I don't think I need a manual switch/button for H range driving cause I've done some pretty nice 4wd tracks where I never even engaged 4wd and it got through every time so I'm definitely happy with that and knowing that I have L range, too.

Carlton draught

No worries mate. You need to read up on how differentials work, especially the center diff in the transfer case. You also need to install a manual center diff lock switch in your '97 because the way they come stock, the center diff will only lock in low range.

 

[crooozer]

UPDATE** The truck rolls real nice, and with the CDL engaged it is a little less agressive in terms of ripping grass up, it will only do half the damage it used to. So with the VC it used to leave bit tears of grass sections when turning tight every 4-5cms and now the frequency of the tear has halved and so has the size of the tear mound.

In terms of people reporting driveline clunk after pulling their VC, I have LESS clunk, in fact, the clunk is actually GONE for me..!
Maybe I fluked it by putting both the driveshafts back on in 'tighter' positions. FWIW I could also see marks on the shaft that the VC came out of that indicate wear, it's still ok but definitely took a toll on the driveline. And thats just that one section so god knows how the rest look.

All in all, I'm happy. Haven't gone off road yet but I still have CDL if it gets rough.

 

[crooozer]

Also, I'd like to add: You should consider replacing your rear output shaft seals and bearings while you have the back of the T-case open. It's a real pain to do it all over again and really a waste of time, too. Plus I find that you stress the bolts and it's very possible you will round off at least one of the driveshaft bolts because they are VERY tight.

You should also take a look at your speedo sensor, chances are that if it is more that 6-7 years old it will require a new O-ring and possibly seal. But that can be done with the transfer case up and running, same general area though.

 

[l1coeea9]

Thanks for reeminding me that my 91 doesn't have a VC.

It (the VC) rids the driveline clunk? Why would Toyota want to do that?

 

[crooozer]

It does more stuff than that man. But then again, if you read one of my posts above a few pots here, you'll see that removing the VC got RID of my clunk.. Go figure.
If it were placed there to rid clunk, why would Toyota want to do that? Because it adds pressure and noise where there shouldn't be.

 

[crooozer]

With all the common misconception, I thought I'd post this short article I found online below:

The viscous coupling is often found in all-wheel-drive vehicles. It is commonly used to link the back wheels to the front wheels so that when one set of wheels starts to slip, torque will be transferred to the other set.
The viscous coupling has two sets of plates inside a sealed housing that is filled with a thick fluid, as shown in below. One set of plates is connected to each output shaft. Under normal conditions, both sets of plates and the viscous fluid spin at the same speed. When one set of wheels tries to spin faster, perhaps because it is slipping, the set of plates corresponding to those wheels spins faster than the other. The viscous fluid, stuck between the plates, tries to catch up with the faster disks, dragging the slower disks along. This transfers more torque to the slower moving wheels -- the wheels that are not slipping.
When a car is turning, the difference in speed between the wheels is not as large as when one wheel is slipping. The faster the plates are spinning relative to each other, the more torque the viscous coupling transfers. The coupling does not interfere with turns because the amount of torque transferred during a turn is so small. However, this also highlights a disadvantage of the viscous coupling: No torque transfer will occur until a wheel actually starts slipping.
A simple experiment with an egg will help explain the behavior of the viscous coupling. If you set an egg on the kitchen table, the shell and the yolk are both stationary. If you suddenly spin the egg, the shell will be moving at a faster speed than the yolk for a second, but the yolk will quickly catch up. To prove that the yolk is spinning, once you have the egg spinning quickly stop it and then let go -- the egg will start to spin again (unless it is hard boiled). In this experiment, we used the friction between the shell and the yolk to apply force to the yolk, speeding it up. When we stopped the shell, that friction -- between the still-moving yolk and the shell -- applied force to the shell, causing it to speed up. In a viscous coupling, the force is applied between the fluid and the sets of plates in the same way as between the yolk and the shell.

 

[crooozer]

And another:

A viscous coupling is a part found in the drivetrain of an all wheel drive vehicle. Although “all wheel drive” is a term that is used rather loosely, technically speaking an all wheel drive vehicle is one that runs in two-wheel drive under normal conditions, but automatically switches to four-wheel drive if the front wheels start to slip. The viscous coupling is basically the part that tells the back wheels when to kick in.
The viscous coupling is based on the principles of a hermetic container. The viscous coupling is basically a cylinder with a shaft, or axle, protruding from either end. Inside, there are plates attached to each shaft so that they spin alongside each other. One axle and set of plates turn in time with the front wheels, and the other axle and set of plates turn in time with the back wheels.
The truly ingenious feature of the viscous coupling is the fluid inside it, which is what allows the coupling to do its job and switch to four-wheel drive when needed. When the friction is low, this fluid flows very easily; however, when the friction increases, the fluid stiffens up, creating resistance instead of lubrication. Once the friction drops off again, the fluid will go right back to its thinner state.

 

[ElPolloBlanco]

Ok I'm doing this with my 4 days off this weekend. Probably tomorrow. I understand pretty much everything and have only 2 questions. 1. Should the separator be removed also or no? And 2. What kind of snap ring pliers will I need? Any type will work I'd assume, though I don't see any holes to put the pliers into. Thanks in advanced.

 

[Frankencruiser]

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This pair worked perfect for me. I'm not sure what you mean by the separator.
Good luck