Clunk (1 Viewer)

[Russ in California]

I have a good clunk in my 91. I understand about the rear output shaft but my question is will heavier gear oil (85-140) make any difference at all?
Don't want to tear into the beast. Handbrake's looking for something with a little better milage.
thanks,

 

[cruiserdan]

Have you checked the drive flanges Russ?

You will have some "slop" in the transfer, diffs and often the drive flanges, especially on 91-92. a little in each area adds up fast.

In order to check the drive flanges I find it easiest to remove them and then flip them inside-out on the stubshaft and then try to rotate them from side-to-side. You should have very little movement in that axis.


D-

 

[CJF]

I have a good clunk in my 91.

So do I. So do pretty much all 91-92 owners. Haven't heard of a single case yet where it led to serious problems, *if* no other symptoms are present. (Note: This ONLY applies to 91-92's)

Personally, I wouldn't go to a non-recommended gear oil weight even if it did help; but hey, try it if you want.

Curtis
91FJ80
230K, clunking since I got it at 100K in 1999.

 

[Russ in California]

Have you checked the drive flanges Russ?

You will have some "slop" in the transfer, diffs and often the drive flanges, especially on 91-92. a little in each area adds up fast.

In order to check the drive flanges I find it easiest to remove them and then flip them inside-out on the stubshaft and then try to rotate them from side-to-side. You should have very little movement in that axis.


D-

Dan, yes, when the birf's where repacked. Seemed to help just a smidge for a while.
Thought maybe the outer splines on the birfs might me bad too causing most of the prob and then reworn the new drive plates. I had hoped that bad plates and birfs would cure it but seems most people have the problem in the transfer. Be cheaper and easier if it was up front. Guess I could try that but since we're probably going to sell it not sure if I want to dump $$ into it now.
thanks,

 

[CJF]

seems most people have the problem in the transfer.

Russ,

Where are you getting this information, and what exactly do you suspect the problem to be?

I'm tellin' ya: 91-92 80's clunk. Put it in reverse, "Slam-clunk!" Put it back in drive, "Slam-clunk!" Let off the gas anything other than as gently as possible, "clunk." Get back on the gas, "clunk." Clunk, clunk, clunk, clunk, clunk!

It's generally believed that it's just a result of all the accumulated AWD slop, and, in fact, I'm starting to think the mysterious VC in the later models is there for no other reason than to reduce this.

As for the output shaft: Are you talking about spline wear and the McNamara gear solution? That is a 62 series issue, and AFAIK (with lots of time on the 3FE list discussing this) a non-issue on our rigs.

Here's what we tell folks who write in with this question on 3FE:

62 series: Fear the clunk.
80 series: Embrace the clunk.

Curtis

 

[Russ in California]

Russ,

Where are you getting this information, and what exactly do you suspect the problem to be?
I'm tellin' ya: 91-92 80's clunk. Put it in reverse, "Slam-clunk!" Put it back in drive, "Slam-clunk!" Let off the gas anything other than as gently as possible, "clunk." Get back on the gas, "clunk." Clunk, clunk, clunk, clunk, clunk!
It's generally believed that it's just a result of all the accumulated AWD slop, and, in fact, I'm starting to think the mysterious VC in the later models is there for no other reason than to reduce this.
As for the output shaft: Are you talking about spline wear and the McNamara gear solution? That is a 62 series issue, and AFAIK (with lots of time on the 3FE list discussing this) a non-issue on our rigs.
Here's what we tell folks who write in with this question on 3FE:
62 series: Fear the clunk.
80 series: Embrace the clunk.
Curtis

The info is comming from the 80's and 3FE boards. I don't know exactly what the problem is. New drive plates seemed to help a smidge but didn't last long.
Has anyone had the clunk develop into a full blown break?
Kind of a lame situation for LC's to be in IMHO.

 

[CJF]

New drive plates seemed to help a smidge but didn't last long.

Yup, at least one 3FE'er (Jon Held) has reported the same thing.

Has anyone had the clunk develop into a full blown break?

I honestly don't think so, but we'll see.

Kind of a lame situation for LC's to be in IMHO.

Aw, now that just hurts!

Maybe it's possible to add a VC?? Wouldn't make much sense if you're selling it though...

Cheers,

Curtis

 

[Russ in California]

Pardon my ignorance, VC?

 

[CJF]

Viscous coupler.

Part of 93-7 TC's. (Oops, I mean transfer cases. ) If you look at the threads where it's been discussed, no one seems to know exactly what its purpose is. Even the big guns tend to write vague things like "Well, it's meant to, sort of, to a limited degree, keep the T-case from..."

S'pose I'll draw anyone out with that crack? ;p

Curtis

 

[Beast]

Try enguaging the centre diff lock and see if it goes away.... The reason im asking is I too have the same problem with alot of slop but it is minimal when the CDL in on. Hows that for throwing a wrench into the mix.

 

[Ted44]

Viscous Coupling. http://auto.howstuffworks.com/differential9.htm

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.

Now, we can ask about the life of the components of this system. What is the "viscous fluid" and how long does it last? Oh sh!t...

 

[Jason Andrews]

yep

Yeah, I usually leave mine rolling a little in reverse, not bring it to a complete stop before kicking it into drive. That keeps it from clunking most times. It sounds like it is coming from the rear ds and diff, but actually if you pull the front ds out and lock the CDL it will go away. It is the viscous coupler thing that creates play in the t-case between the driveshafts. It will most likely not get any worse. Not much you can do. no harm done. No worries

 

[Ted44]

Wait, No VC before '93... right?

 

[CJF]

Wait, No VC before '93... right?

Correct.

Like I said, I think the lack of one that contributes to the 91-92 clunk, since it sure seems to me it's going to act like a dampener, regardless of its intended function.

Curtis