Viscous coupler gone! Yes. (1 Viewer)

['74 UA FJ]

Yes, I think it would lead to better comprehension of a PT 4WD (and a locked center diff on an 80) since there is no diff in it....


forget it though, someone will find way too much to get confused about with that analogy...

No. I don't understand why you want to call a part time transfer case a PTO. PTO stands for power take off which is used for winches, generators and other stuff. Not for front axle drive.

 

[UTREDROK]

It is weird, the PO maintenance history is like this... Majority of work done by the same 'local' mechanic.

120K had L front axels done/seals rings etc....
start to complain of front end tightness.
125K has R front axel done
130K quotes from dealer to repalce T-Case ($3200)
131K local shop R&R T-case with a used one ($750) it must have been a bad VC in the used t case, or the shop used the old VC in the new T-case??

131K -146K two more front axel jobs under warentee from same local shop. Last one was 1000 miles ago... in November. I think they just didn't know what to look for and definitly didn't read IH8MUD! You would really think they could have figured it out, but their ignorance is my benefit.

Now it's mine... I feel like I paid too much because I didn't realize something was wrong for about a day or so. But really, I am happy with it, and at $8900 it was a good deal, but could have done better with leverage...

 

[-Spike-]

I have my doubts that the front axle issues were caused by the faulty VC. My wife's has been siezed since I bought the truck at auction ~20K miles ago with no issues other than chirping the tires around corners. Four axle 'jobs' done in 16K sounds like something else was wrong. There is at least one user on this board that runs his 80 with the center diff locked all the time, and claims no problems. I have always believed this condition would add wear to the drivetrain, but not cause that much damage. Exactly what were the symptoms, why was the axle re-'done' so many times? Sorry if that info is in another thread, if so I wasn't following it.

-Spike

 

[CJF]

I have my doubts that the front axle issues were caused by the faulty VC. My wife's has been siezed since I bought the truck at auction ~20K miles ago with no issues other than chirping the tires around corners. Four axle 'jobs' done in 16K sounds like something else was wrong.

Don't mean to speak for the OP, but I think all those axle jobs were just misguided attempts to fix the seized VC issue. My guess is that none (or maybe one) of those rebuilds were necessary, nor did they accomplish/cure/solve anything whatsoever.

Curtis

 

[UTREDROK]

I've thought of that...

I have thought that there maybe an underlying issue, but I didn't like thinking about that much...to much to worry about in a 2 week old rig. The front end was real creaky/poppy in the turns before the VC removal. It sounded like it was 'deeper' than the birfs.... and it's gone now. All that drivetrain torque had to go somewhere and I think the front took the brunt of it.

As for now, everything seems to be running like a top...thank heavens. No work tomorrow so time to play with it now that I can drive it!

 

[BLACKGOLD]

Congrats UTREDROK! Lets get that thing out and off the pavement sometime!

 

[alia176]

VC is gonzo!
So... no one read my updated thread. Here is a new one.


Slapped the case back together, and drove it home happy to have saved $1000 by not buying a new VC for it. I was even happier to get home and find a box of goodies from C-Dan waiting for me. (thanks again and hope your feeling better) Installed the CDL switch and everything is working like a dream.

So am I to understand that you drove home w/o a VC? So, you have no automatic center lock for AWD operation but I wonder if the front DS is still getting any power? If it's this easy then why is there a Part Time kit?

 

[tntoyota]

No. I don't understand why you want to call a part time transfer case a PTO. PTO stands for power take off which is used for winches, generators and other stuff. Not for front axle drive.

WTF is the difference? ....

A PT TC for lack of better words IS IN FACT A PTO!

A PTO can only transmit what the drive to it, can do. (=2/ 1:1...ONLY, sorta like a TC I know of )


A independent PTO can run in a broad range of rpm's separated from how the force was applied to it.

Power take-off - Wikipedia, the free encyclopedia

My point is the concept of reaching down pulling a leaver, in a PT 4WD on a hard surface you cannot do this. Some new LC owners KNOW this, but lose all concept when they buy there first FT (AWD) TC.
Some think its 4WD and 4WD it is not. It throws the hell out of some, and makes them

(hence lets call it something else only for a better mental grasp)

A locked (center diff) is the SAME as a PT, TC IN HI4 or LOW4 (trust me.)

An UNlocked FT TC in low or high IS NOT TRUE 4WD, (trust me)


They both share the "transfer case" designation but that is where the similarity's end.


If you didnt have to call a spade a spade this would not matter, but since its a source for MAJOR CONFUSION.....

 

[tntoyota]

ya'll might orta take me off of H8 mail once and a while, ya mighta learnt sumpn

 

[riberware]

Is there any CONS with the removal of the VC and leaving the center diff open???

ABS still works after this mod???

I think I have a seized VC, and replacing it is not an option.




Ricky

 

[toylndcrusr]

Ok, I am apparently having a some kind of relapse or something here because now I am confused. I though that the VC acted as a differential for the TC, and without the VC power only went to the rear axle unless the the TC was locked. If that is the case, then removing the VC and adding manual hubs would make the FZJ80 "four wheel drive" like my old 4Runner right? See, it was my understanding that to make the FZJ80 part time four wheel drive you had to add hubs and a CDL switch and remove the front drive shaft. But with a CDL switch and no VC, couldn't you just add manual hubs? I am assuming that with the TC unlocked and no VC power only goes to the rear wheels. Is this correct? If I am wrong about all this, can someone please explain? Thanks.

 

[riberware]

Ok, I am apparently having a some kind of relapse or something here because now I am confused. I though that the VC acted as a differential for the TC, and without the VC power only went to the rear axle unless the the TC was locked. If that is the case, then removing the VC and adding manual hubs would make the FZJ80 "four wheel drive" like my old 4Runner right? See, it was my understanding that to make the FZJ80 part time four wheel drive you had to add hubs and a CDL switch and remove the front drive shaft. But with a CDL switch and no VC, couldn't you just add manual hubs? I am assuming that with the TC unlocked and no VC power only goes to the rear wheels. Is this correct? If I am wrong about all this, can someone please explain? Thanks.

The VC is kind of a locker that divides power in certain % to the front or the rear depending on the situation (ie, 80% rear 20% front), without the VC the center diff behaves just like an open differential that sends "all" the power to the rear or to the front depending on the situation

 

[tntoyota]

The VC is kind of a locker that divides power in certain % to the front or the rear depending on the situation (ie, 80% rear 20% front), without the VC the center diff behaves just like an open differential that sends "all" the power to the rear or to the front depending on the situation

ok, I'm not gonna requote you and you are SOMEWHAT correct

But, it should read this though:

The VC is kind of a LIMITED SLIPthat divides power in certain % to the front or the rear depending on the situation (ie, 80% rear 20% front), without the VC the center diff behaves just like an open differential that sends "all" the power to the rear or to the front depending on the situation

because class, a locker, an open diff and a ltd slip are all COMPLEATLY DIFFERENT

 

[tntoyota]

Ok, I am apparently having a some kind of relapse or something here because now I am confused. I though that the VC acted as a differential for the TC, and without the VC power only went to the rear axle unless the the TC was locked. If that is the case, then removing the VC and adding manual hubs would make the FZJ80 "four wheel drive" like my old 4Runner right? See, it was my understanding that to make the FZJ80 part time four wheel drive you had to add hubs and a CDL switch and remove the front drive shaft. But with a CDL switch and no VC, couldn't you just add manual hubs? I am assuming that with the TC unlocked and no VC power only goes to the rear wheels. Is this correct? If I am wrong about all this, can someone please explain? Thanks.

OMG!! I just reread that whole thing! aaggghhhhh!




Do you know HOW a standard differential, a cars rear end works?

Now, in your mind picture that diff placed longitudinal, perpendicular to the vehicle.

NOW imagine each of the two tires, instead of tires, as drive shafts.

NOW, picture in your mind those drive shafts connected to AGAIN another set of axles (as we are talking about 4WD you need two diffs one std, and one steerable)


place a diff between two diffs

NOW, what function does an OPEN diff serve? (rotational force follows the diff with the least resistance)


play with all the variables you want, open your mind you are now on your way.


A VC is the CENTER DIFFS LTD slip.

 

[Beowulf]

... but I wonder if the front DS is still getting any power? If it's this easy then why is there a Part Time kit?

The front DS is getting whatever power (torque) that was designed into the transfer case. I have heard 50/50 and I have heard 40/60 and I have heard 20/80. I would believe 50/50 or close to that. The VC is the limited slip component of the center diff and will transfer a portion of the torque to the F if the R is slipping (turning faster) and it will transfer a portion of the torque to the R if the F is turning faster than the R.

Links to NCF pages.

So the answer to your 2nd question is "no, it is not this easy" and the PT kit is required (and complex) because it isn't this easy.
-B-

 

[-Spike-]

The front DS is getting whatever power (torque) that was designed into the transfer case.
-B-

Well, that's completely wrong. There's no 'percentage' (not Beo's word, but mentioned by other posters, i.e: 80/20, 60/40, 50/50 et al) at all. It's a differential. It applies ALL of the power to BOTH axles, the same way the axle differential applies ALL the power to BOTH wheels. If one slips, ALL the power is lost to that slippage. A differential does not 'split' power, it allows speed 'differential', hence the name. The VC limits the amount of slippage, or differential, allowed. It is, truly, a slip limiter. A locker is a slip eliminater. Neither the center diff, VC, or locker have a clue as to which end is the front or rear, and they treat both ends the same.

People keep mentioning this magical 50/50 split at the diffs- that's misleading. The diffs don't send half the power (or any percentage of power) to any place, they send ALL the power to everywhere. Think of it like a 'T' in a water line. All the water pressure is available anywhere in the system, but if a leak develops the pressure will be lost through it depending on how big the leak is. If it's a small leak, there will still be pressure elsewhere in the system. If the water line at one leg of the 'T' is completely open, all the pressure will be lost there. On a car axle, if one tire slips a bit, there will still be power at the other wheel. If one wheel completely loses traction, the other wheel has no power. Same thing in the center diff without the VC.

-Spike

 

[CJF]

Holy Phuque...

 

[Doc]

I think maybe we need to start a new thread on how differentials operate. I'm seeing some really surprising posts from folks that should know better.

Yes, you can drive your LC without a viscous coupler. Just don't loose traction to ANY wheel, or you'll be dead in the water. This is different than driving without a driveshaft (front OR rear) where you will need to LOCK the center diff to move at all. As long as you have the drive shafts in place the axles will turn without the VC. Power will be split equally until one wheel slips (ice, gravel, etc...) at that point all of the power (because the VC is removed) will go to the slipping wheel. Your truck will be no different than a 2 wheel drive car at this point. Then, you can lock your center diff, and it will be the same as most conventional 4WD vehicles, and power will be split (50/50) to both axles and you'll be able to move again, unless the other axle has a spinning wheel. I suppose at this point you could lock the axle lockers and have true 4WD- even on wet ice you should be able to move (slowly) at this point.

 

[toylndcrusr]

Right right right.....sorry about the total brain fart. Got it! Thanks guys. This kind of makes me wish I could put a TC from a 4Runner or Taco or Tundra in my Cruiser just to save the wear on the birfs.

 

[alia176]

I think maybe we need to start a new thread on how differentials operate. I'm seeing some really surprising posts from folks that should know better.

Yes, you can drive your LC without a viscous coupler. Just don't loose traction to ANY wheel, or you'll be dead in the water. This is different than driving without a driveshaft (front OR rear) where you will need to LOCK the center diff to move at all. As long as you have the drive shafts in place the axles will turn without the VC. Power will be split equally until one wheel slips (ice, gravel, etc...) at that point all of the power (because the VC is removed) will go to the slipping wheel. Your truck will be no different than a 2 wheel drive car at this point. Then, you can lock your center diff, and it will be the same as most conventional 4WD vehicles, and power will be split (50/50) to both axles and you'll be able to move again, unless the other axle has a spinning wheel. I suppose at this point you could lock the axle lockers and have true 4WD- even on wet ice you should be able to move (slowly) at this point.

Good info. The part time kit forces all of the power to go to the rear DS until the CDL button is pressed. At that time, front and rear DS receives power 50/50.