Should I replace my Viscous Coupler as PM? (1 Viewer)

[scottryana]

No you are confusing, just removing the VC and removing it and doing the part time conversion.

If you just remove it you operate as an open differential


If you remove it and do the part time you are 2wd or locked 4wd.

Ummm.....that's not what @Dave 2000 said........

 

[Tools R Us]

Ummm.....that's not what @Dave 2000 said........

The VC is just an ineffective limited slip for the center diff, no other mods are necessary, simply removing it leaves AWD without the ineffective limited slip.

 

[BILT4ME]

The VC is just an ineffective limited slip for the center diff, no other mods are necessary, simply removing it leaves AWD without the ineffective limited slip.

So, based on what you stated earlier, I could literally be on snow/ice and have only ONE wheel spinning until I engaged the CDL, at which point I will then have a minimum of one rear and one front (two total) wheels spinning. Right?

I'm used to the old TC's that are either 2WD or 4WD (Rockwell T221) and no slipping or differential in the middle.

 

[Dave 2000]

The rig is essentially one wheel drive stock, other than being a clunk dampener, the VC is basically useless. The '91 & '92 FJ80 and 100 series use the same family of transfer, but don't have the VC. Why did Toyota remove it in the 100,,, likely because it's just an overpriced/over engineered/not very effective, clunk dampener?

I could not have put it any better!

You do NOT lose the differential...period! See the VC as an LSD in your rear differential but in the centre instead. If you think how many LSD's fail but the actual differential continues to function normally. The VC fail mode is to seize up and then there no slippage, it is as if the CD is engaged, tyres squeal on corners and the transmission binds up, it acts like a badly setup LSD.

Throw it in the bin and the centre differential remains intact but completely open, you need to engage the CDL to lock the two drive shafts together.

regards

Dave

 

[LiftedLexus]

Ok so now it seems there is no consensus on weather to leave it or remove it???Without the VC in an AWD truck (not part time) if you loose traction and have the center diff unlocked one wheel can just be spinning right? As opposed to with the VC one wheel on each axle will be spinning if traction is lost...

Based on earlier posts and Dan's advice I was convinced to just leave it alone and replace it if it ever seizes up because I will NEVER go to part time. So help me decide guys.
Option 1: leave as is
Option 2: replace VC as pm
Option 3: remove VC and keep the truck AWD

Thank you for all of the opinions. Keep them coming!

 

[Dave 2000]

So, based on what you stated earlier, I could literally be on snow/ice and have only ONE wheel spinning until I engaged the CDL, at which point I will then have a minimum of one rear and one front (two total) wheels spinning. Right?

Correct!

regards

Dave

 

[Dave 2000]

Ok so now it seems there is no consensus on weather to leave it or remove it???Without the VC in an AWD truck (not part time) if you loose traction and have the center diff unlocked one wheel can just be spinning right? As opposed to with the VC one wheel on each axle will be spinning if traction is lost...

Based on earlier posts and Dan's advice I was convinced to just leave it alone and replace it if it ever seizes up because I will NEVER go to part time. So help me decide guys.
Option 1: leave as is
Option 2: replace VC as pm
Option 3: remove VC and keep the truck AWD

Thank you for all of the opinions. Keep them coming!

Trying to keep up with the posts crossing as I am typing.

Option 1 and if it packs up THEN option 3, regardless of what you do the vehicle WILL remain AWD.

regards

Dave

 

[BILT4ME]

Correct!

regards

Dave

OK Thanks! You'll have to excuse my friend.....He's a little slow.......

 

[Delancy]

Based on Dan's advice...

So help me decide guys.
Option 1: Listen to CDan, unquestioningly.
Option 2: See option 1.

I vote "Option 1".

 

[Tools R Us]

... Without the VC in an AWD truck (not part time) if you loose traction and have the center diff unlocked one wheel can just be spinning right? As opposed to with the VC one wheel on each axle will be spinning if traction is lost...

Correct, kinda. The VC is a silicone fluid coupling, so never "locks", is only capable of transferring so much torque. When one drive shaft turns significantly faster than the other, the VC attempts to transfer some drive to the other. This effect is called "humping" by Toyota and is brief (very) and not very powerful, so in real world application, not very useful.

Can't help with the "what do I do thing" that is up to you. Play with it and see if it's worth anything to you? Drive into a ditch or obstacle where a tire is off the ground, spinning, attempt to drive out. Should feel it attempt to pull, then stop, repeat, if it's any kind of obstacle at all will be ineffective, but will be able to feel it work. Then lock the center and drive right out. They work, kinda, but in real world use, the CDL is far more effective, useful.

That said, have seen very few fail, and most of them were abused, run without a drive shaft, hugely differing tire sizes, etc. So if it's not causing any problem and there is no need to be in the transfer, I wouldn't mess with it.

 

[Dave 2000]

I vote "Option 1".

Absolutely! Mine has 233,000 miles on it and is in the garage as a spare if it is needed, they are very reliable anyway, if I didn't it would be thrown in the bin and the TB put back together without one. What is good about this thread is the OP has his answer and also enlightens not only new owners and also many who have misunderstood the nature of the VC.

regards

Dave

 

[aim]

...
That said, have seen very few fail, and most of them were abused, run without a drive shaft, hugely differing tire sizes, etc. So if it's not causing any problem and there is no need to be in the transfer, I wouldn't mess with it.

As a somewhat related aside:

If you jack ONE wheel up and put the transmission or transfer case in Neutral, on an 80 without the VC it is rather easy to spin the wheel (spinning the axle shaft on that side and one of the driveshaft). On a vehicle WITH the VC, you will experience some resistance due to the VC doing its thing. As I understand it, a failed VC will actually prevent you from turning the wheel.

My question is: when it comes to turning the wheel, how much effort is too much? One finger to turn a 33" tire? Both hands, trying to turn the brake rotor?

 

[dogfishlake]

The thing the AWD gives for me that i love, is in a situation like i get every day of the winter on my driveway, it is very steep with little room to run at it. If I don't remember to put the truck in 4wd (like my wife's old 4th gen 4runner) getting to the top wont happen if it's snowing. With the cruiser(s) and the wife's current 5th gen 4runner limited (the only one with AWD), no problem ever, just climbs away. One trip sliding down backward trying to keep her straight did it for me, i forgot I was in the 4runner and not my cruiser. So anyway, that would seem to be the AWD benefit, maybe rainy expressway at 70 mph too?

 

[LiftedLexus]

The thing the AWD gives for me that i love, is in a situation like i get every day of the winter on my driveway, it is very steep with little room to run at it. If I don't remember to put the truck in 4wd (like my wife's old 4th gen 4runner) getting to the top wont happen if it's snowing. With the cruiser(s) and the wife's current 5th gen 4runner limited (the only one with AWD), no problem ever, just climbs away. One trip sliding down backward trying to keep her straight did it for me, i forgot I was in the 4runner and not my cruiser. So anyway, that would seem to be the AWD benefit, maybe rainy expressway at 70 mph too?

That is a good point and is exactly why I am not part timing my truck. Toyota made their top of the line SUV's AWD for a reason. However you are misunderstanding the thread, we are not talking about part timing the truck. If you remove the VC your truck is still AWD. The VC is essentially a limited slip center differential when your actual center diff is unlocked (locking the center diff takes the VC out of the equation and splits the power evenly between axles). So if you removed your VC your truck would still be AWD but when going up your driveway you would have to engage your CDL bc all of the power could go to one tire if traction was lost with the VC deleted (if your center diff is unlocked). I hope that makes sense.
Anyways I have decided to go with option 1. Feel free to convince me otherwise anybody! Thanks...

 

[Tools R Us]

As a somewhat related aside:

If you jack ONE wheel up and put the transmission or transfer case in Neutral, on an 80 without the VC it is rather easy to spin the wheel (spinning the axle shaft on that side and one of the driveshaft). On a vehicle WITH the VC, you will experience some resistance due to the VC doing its thing. As I understand it, a failed VC will actually prevent you from turning the wheel.

My question is: when it comes to turning the wheel, how much effort is too much? One finger to turn a 33" tire? Both hands, trying to turn the brake rotor?

This is very subjective, have seen VCs that are tight, difficult to turn by hand, some that are comparatively loose, all worked, hard/impossible to judge condition with that test? I test them by driving, on a smooth surface (like a gas station) should be able to turn without excessive tire squeal. When it fails, the steering becomes stiff, locking, unlocking the CDL makes little/no difference.

 

[Delancy]

Toyota made their top of the line SUV's AWD for a reason.

Yes, because there wasn't any other way to implement ABS without it.....and why they introduced the viscous coupler, for the 'Merican market.

Betting if Toyota had it to do over, there'd be ADDs in the front diff.

 

[Tools R Us]

That is a good point and is exactly why I am not part timing my truck. Toyota made their top of the line SUV's AWD for a reason. However you are misunderstanding the thread, we are not talking about part timing the truck. ...

Agree, AWD has traction/handling benefits, personally would not remove it.

If you remove the VC your truck is still AWD. The VC is essentially a limited slip center differential when your actual center diff is unlocked (locking the center diff takes the VC out of the equation and splits the power evenly between axles). So if you removed your VC your truck would still be AWD but when going up your driveway you would have to engage your CDL bc all of the power could go to one tire if traction was lost with the VC deleted (if your center diff is unlocked). I hope that makes sense. ...

Agree, with one significant distinction. One way to explain the VC is as a limited slip, but that isn't really correct. Most limited slips work by the power/torque difference between shafts, so will stay "on" as long as the power difference exists. The VC works on speed difference, the spinning of the parts inside make it work, if it's successful, stops the speed difference, so it relaxes, may not of solved the traction problem, so starts over again. So, a limited slip is more "on" until the job is done, the VC is "on", "off", repeat, herky jerky. If the traction aid need is very brief they can be help, most cases not really, best to lock the CDL.

Anyways I have decided to go with option 1. Feel free to convince me otherwise anybody! Thanks...

Agree, best option, overall they are very reliable. If it ever fails, I wouldn't pay what they are new, so decide if you want to remove, or they are commonly available used.

 

[Tools R Us]

Yes, because there wasn't any other way to implement ABS without it.....and why they introduced the viscous coupler, for the 'Merican market.

Lots/most vehicles have ABS without AWD, the rings could have easily been put on the hubs, they have nothing to do with each other. The VC has been around for a longtime, IIRC, came out in the Audi Quattro, was highly touted tech in the day. Toyota only ran it for a few years, likely figured out it isn't all of that.

Betting if Toyota had it to do over, there'd be ADDs in the front diff.

I highly doubt it, AWD has significant benefit, so would be on their flagship SUV. ADD tech predated the '80 design, could have easily been incorporated if that is what they wanted.

 

[Whileemptyheadsdream]

Best PM is to pull the VC and toss it off to the side of the carport, by the F blocks and three speed/solid cases, where it belongs.

If it weren't for the discriminating butt dynometer of the pansy ass Americans, it wouldn't be there, to begin with, but even the MOST discriminating will never know its gone.

Now THATS what I'm talkin about..! Don't candy coat It next time Delancy, Tell It like It REALLY Is..! You made my day.!

 

[BILT4ME]

I did a specific study on this technology (VC) when I was in college in 1986. This was brand new technology in testing at that time and was being touted as being designed to replace the transfer case and be able to make all cars AWD with minimal expense and weight additions.

I did tons of research (there wasn't any Interwebs then......) so I was calling tech shops, specialty 4x4 shops, and anyone I knew that knew someone that had a connection to automotive manufacturers to try to find out how they worked and what the intent was. I was very into 4x4 at that time, having built my own 4x4 in high school.

No, viscous couplers have no direct relationship to ABS. What the VC WILL allow is better control of ABS, now that we have computers and a sensor on each wheel and pressure sensors to control all of it.

ABS was in its early conception in the mid 1980's, as only the high-end cars were coming out with it, but absolutely no 4x4's, and even 2WD pickups only got it on the rear axle to prevent the rear from sliding out during heavy braking.

As far as being worried about "breaking things" when the front and rear are "locked together", that's the way ALL transfer cases were designed prior to about 1990. The early ones were gear-driven (specifically the Rockwell T-221) and the later ones were chain driven and you had hi range 4x4, Hi range 2WD, Neutral, and Low range 4x4. The front and rear DS turned the same speed in all cases and were locked together. When we would turn corners with the hubs locked in, the truck would "hop" or the front tires would squeal as you made the corners. Realize that at that time, the closest thing to an SUV was a Chevy Suburban, a K-5 Blazer, a Ford Bronco, or a Dodge Ramcharger. These were designed as a truck first, with some luxury, but it was still understood that the people driving them had a specific need for one of these and understood what NOT to do. (tight corners on pavement while locked in 4x4)

Once the tax laws helped folks figure out that they could buy extended cab pickups or Blazer, Ramchargers, or Broncos and still deduct them as a TRUCK, folks started buying MORE of them. When sales went up, so did the problems, because Sally housewife was driving a TRUCK in 4x4 and didn't have a clue that she wasn't SUPPOSED to be able to do that. The demographics of a 4x4 owner started to change.

So, eventually, the VC was invented to help cushion the driveline (clunk damper) and to make it so those folks that didn't have a clue could drive what was still perceived as a truck and not complain and not break it.

Now, here we are, 29 years later, and we've figured out that for the HD work that we want our truck to do doesn't do well with a VC. But I'll guarantee that if you let your drive the truck without a VC, there will be either bitchage or breakage at some point, because most don't care, they just want to drive the truck and not have to worry about it.

What's my point? I was pissed because I got a C- on the paper because my instructor didn't think I put enough research into it and he didn't see the relevance to the drive line design we were working on with agricultural equipment. pppfffttthhttt!!! What did HE know?!?!?!?

If you look at the 4x4 technology that has developed over the years from when Willys first started using it during the war, lots of things have changed, but a few have remained the same. There were a few good ideas over the years, but there were more bad ideas (self-locking front hubs on GM for "full-time 4WD") Now that we can throw thousands of HP at a 4x4 and make it do all sorts of stupid things, we help develop new, innovative ways of thinking and we can make it all better. Who knows, maybe in the next 29 years, we'll have FLYING cars!

Thanks for reading!