Viscous Coupler removal and AWD

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I would keep the VC.

With all open differentials, the maximum torque that can propel the vehicle is equal to the tire that has the LEAST traction of all four. So if one tire is slipping on ice but the other three tires are on dry pavement, all of the engine's power/torque/rpms will be routed to that one slipping tire on ice.

If you have a center VC in that same situation, you will not get stuck.
 
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pulse98 said:
I would keep the VC.

With all open differentials, the maximum torque that can propel the vehicle is equal to the tire that has the LEAST traction of all four. So if one tire is slipping on ice but the other three tires are on dry pavement, all of the engine's power/torque/rpms will be routed to that one slipping tire on ice...
Let me try one more time. Open diffs distribute torque equally, always. Open diffs will never route all of the torque to a single wheel, slipping or not.

Power is a different story, if only one wheel is turning, then that wheel is indeed getting all of the power. Distinguishing between power and torque makes it much simpler to explain and understand how a differential behaves. Power = Torque x RPM.

As many have stated, the ability of a locker, or a viscous coupler, to bias torque, is the mechanism that can enable forward motion when one or more wheels loose traction.
 
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For my sake, let's simplify, let's take a 2wd truck with an open diff. One tire is on dry pavement, the other is on ice.

Let's say the tire to ice interface has a coefficient of friction of 0. That means the torque to that tire will be 0.

Since open diffs distribute torque equally, then the torque to the tire on pavement will also have to be 0. The truck will therefore not move because 0 applied torque multipled by ANY rpm will equal 0 power transfer.

This is the beauty of VC's...they do not always distrubte torque equally, thus being able to gain traction on the dry pavement while the other tire is slipping on ice.

Gotta love high school physics. I think I'm preaching to the choir.
 
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IdahoDoug

 
 
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Wow, guess I better get my facts straight, eh? I apologize to Rich and anyone I offended by implying you guys were wrong. Looks like I am wrong and that I should have done a bit more research instead of sticking to my long-time assumption on that coupler. Because I participated in a discussion of it a long time ago, I had the matter settled in my mind that it was a simple fluid coupler, and emphatically NOT a VC.

I'm also having a strange sense of deja vu here that I had almost exactly the same disagreement on this exact same item once. (you are all forbidden from doing a search to confirm this, BTW) Clearly I never did check into it. So, I promise I won't do that again, and that I'll look into what is now defined as clearly a true 80 viscous coupler - which ironically is an item I know a lot about.

Regards (sheepishly)

DougM
 

Vlad

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my 2 cents from the non-engineering world:

- If it is in there and works, leave it in there.
- If it is in there and is broken, take it out and save money by not replacing.

Wipe hands on pants, go wheel :)
 
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It really does work to lock up this diff but it has to be hot.
While at Tellico when we would hit a hard obstacle of course everyone stops while others wollow over said rock, ledge etc. My cdl sensor was out and therefore I could not lock it so I was totally dependant on the VC lock the diffs. I would have to work it, people would say "hey your in one wheel drive" then in about 30 seconds of spinning it would heat up and lock up (not immediately but gradually) then she would wollow up whatever ledge was being attempted.
 

Rookie2

 
 
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Rich said:
Power = Torque x RPM.
FYI, the actual equation that relates the transmission of power by circular shafts is:

P = 2 x pi x n x T/60

Where n is the number of revolutions per minute (rpm).

Just in case someone's wanting to crunch some actual numbers here :D.

:beer:
Rookie2
 
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Rookie2

 
 
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pulse98 said:
Since open diffs distribute torque equally, then the torque to the tire on pavement will also have to be 0.
This "open diff distributes torque equally" statement that's been said serveral times doesn't make sense to me. In your 2WD truck with an open diff, if one wheel is on ice, it will spin therefore it's receiving torque or power (whichever you prefer, power is just the rate at which torque is applied). The other wheel does not spin, therefore it is receiving no torque or power. Both shafts only recieve equal torque if there is some kind of limited slip, coupling or locker mechanism engaged, which is not an open diff... right?

:beer:
Rookie2
 
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Rich said:
I'd suggest that Toyota installed the VC for the straight forward purpose of improving the ability of the truck to handle lower traction situations without requiring any technical knowledge on the part of the driver regarding engaging lockers or shifting into low range.

I don't see any reason to remove the VC...
But then why was it removed again in the 100? Why would Toyota deliberately remove it when the VC tcase was prevalent in the 80/market? The 100 I would argue was geared (pun intended) much more to non-``technical knowledge'' folks.

Plus the 100 has ABS of course so that connection doesn't seem to apply.
 
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R2 how abotu this

a rusted solid bolt, I can put 100Ft pounds of torque into it but if it does not turn to no power is put to that bolt,

power = torque x angular speed

so 100 #' x 0 RPM = 0 HP
 

landtank

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Pskhaat said:
But then why was it removed again in the 100? Why would Toyota deliberately remove it when the VC tcase was prevalent in the 80/market? The 100 I would argue was geared (pun intended) much more to non-``technical knowledge'' folks.

Plus the 100 has ABS of course so that connection doesn't seem to apply.

I'd bet the 100 has independent rear wheel ABS. As I said our 80s rear brakes work in unison. Just a guess.
 
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Pskhaat said:
But then why was it removed again in the 100? Why would Toyota deliberately remove it when the VC tcase was prevalent in the 80/market? The 100 I would argue was geared (pun intended) much more to non-``technical knowledge'' folks.

Plus the 100 has ABS of course so that connection doesn't seem to apply.
Just my guess; The later 100 has traction control, the designers probably knew it was on the way and didn't put a VC in the 100 case?
 
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Rookie2,
A limited slip or locker DOES NOT attempt to equalize torque to each shaft. They DO try to equalize shaft speed.

Think about a scenaio where with a 2wd locker has one tire up in the air and the other on firm pavement. As you step on the throttle, 0 torque will be applied to the tire in the air and all the torque will be applied to the tire on the ground. However, both tires will spin at the same speed (rpm).

Rookie2 said:
This "open diff distributes torque equally" statement that's been said serveral times doesn't make sense to me. In your 2WD truck with an open diff, if one wheel is on ice, it will spin therefore it's receiving torque or power (whichever you prefer, power is just the rate at which torque is applied). The other wheel does not spin, therefore it is receiving no torque or power. Both shafts only recieve equal torque if there is some kind of limited slip, coupling or locker mechanism engaged, which is not an open diff... right?

:beer:
Rookie2
 
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Rookie2 said:
This "open diff distributes torque equally" statement that's been said serveral times doesn't make sense to me. In your 2WD truck with an open diff, if one wheel is on ice, it will spin therefore it's receiving torque or power (whichever you prefer, power is just the rate at which torque is applied). The other wheel does not spin, therefore it is receiving no torque or power. Both shafts only recieve equal torque if there is some kind of limited slip, coupling or locker mechanism engaged, which is not an open diff... right?

:beer:
Rookie2
Power is a measurement of work, it is related to torque, but is not interchangeable with torque.

In the example you have given above, both wheels are subjected to the same torque. The torque is sufficient to spin the wheel on ice, it is not sufficient to turn the wheel that has traction, thus, the vehicle goes nowhere.

A limited slip or locker can bias the torque, and provide more torque to the wheel(s) with more traction, than is provided to the wheel(s) with less traction, thus enabling forward motion is situations where otherwise one or more tires are just spinning in place.
 
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IdahoDoug said:
Wow, guess I better get my facts straight, eh? I apologize to Rich and anyone I offended by implying you guys were wrong...
It's just a technical discussion. No need for apologies.
 

Rookie2

 
 
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RavenTai said:
R2 how abotu this

a rusted solid bolt, I can put 100Ft pounds of torque into it but if it does not turn to no power is put to that bolt,

power = torque x angular speed

so 100 #' x 0 RPM = 0 HP
Once the force is applied, if there is no movement in the system it is in static equalibrium. The system is performing no work (no increase in load.. no displacement) and therefore providing no power. The constantly applied force is stored in the system as strain energy (or potential energy).

:beer:
Rookie2
 
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Rookie2 said:
Once the force is applied, if there is no movement in the system it is in static equalibrium. The system is performing no work (no increase in load.. no displacement) and therefore providing no power. The constantly applied force is stored in the system as strain energy (or potential energy).

:beer:
Rookie2

yep exactly that is how the tire that is not spinning can recieve torque but no power from an open diff
 
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