uprated viscous cupplings

aus jd 2703

New member
ok im probably way off but rc cars use silicone oil in their shock absorbers. cause silicone has a high viscocity index so it change viscosity very little for a given temp increase.
they have up to 500 000wt which i believe is some thing like 500 000cst which is very very think.
is that possible to use? the shits not cheap probably $10 fo 60ml
http://www3.towerhobbies.com/cgi-bin/wt ... LXWBN6&P=7
 

MWP

New member
aus jd 2703":3nv2z0ke said:
ok im probably way off but rc cars use silicone oil in their shock absorbers. cause silicone has a high viscocity index so it change viscosity very little for a given temp increase.

:twisted: Thats the exact reverse of what you want viscous LSD fluid to do.
You want it to thicken up a lot when its heated.
 

sleeper

New member
I think i have a idea... Rav 4 is using about the same gearbox as the gt4, and at least the first generation of them have manual ( elctronic) locking on the senter diff.. ( 100% lock)
Might be a way to use a rav 4 center on a st185\205 gearbox and have a way to lock the center?
 

sleeper

New member
MWP":2bcv4yxw said:
That is an interesting idea...
I wonder if itll be strong enough though.


yupp, since the car was made with a 3sfe engine and 4wd ( and elctronic locking) it should fit..
but there is a question if it will hold any power.. ( but my guess is that it will..)
 

st185-sainz

New member
as some of you would like to do a visco unit on exchange, I can offer you to get one done and ship it to you - and you can send it back to me when you fitted the new one! I have 3-5 units in stock and can get them done on order...

how does this sound?! any interests?! I will also post in for sale section!
 

darthripley

Moderator
Mario - how many km's does your ST185 have on it?
Just curious to see how worn the coupling was for you.
Would this fit in an ST205 tranny? That's what I have on our ST185.
It is a low km tranny so I am wondering just how worn the coupling/fluid really is :shrug:

I have a TRD 2 way clutch plate type LSD in the rear which improved handling massively.
Just want to see if it is really worth the work + $$$$ to have this done.
 

st185-sainz

New member
I also have had the 2way lsd in the rear diff at first, but the problem was (what I really noticed after changing the visco) that the car got more sideways but could have more traction to move forward (don't know how to describe it properly...).
I did more than twice the value the stock visco had to improve driveability. I did not change it because it was worn - it is a real improvement! (not only servicing the unit!)

we can set it to a value that you can still use the handbrake or not, as you prefer!
 

st185-sainz

New member
the unit alone is 4kg, so with packaging it will be around 4,5kg (10 pounds?!)

the question was about the postage: I can offer sending the unit for 20EUR to the states (half of the normal price) - this can be done to everybody individually, also If you arrange a group buy!
I'm not very familar with the parcel system in the US, you maybe will find the ceapest way of shipping by searching on your own?!

so the extra shipping costs should not be too much!

If you need more information, do not hesitate to contact me!
 

MWP

New member
So has anyone ever tested their center diff's viscous LSD?

I just did the following:
Car on stands with all wheels off the ground.
Ran up the engine & wheels in 1st gear at ~2000RPM.
Slowly pulled on the hand brake.

Now, if the center LSD is working, the LSD should slip a little, then heat up, and grab which will then try to slow/stall the engine, correct?

I had no problem stopping the rear wheels from turning using the handbrake while the front wheels kept turning
So i gather my center LSD is screwed?
If it makes any difference, its a 205 gbox.
 

gtfour77

New member
If you guys look at the diagram, the front wheels(front diff) are working first...then the power gets transmitted to the center diff (open)...once that strats to slip it gets transmitted to the Viscous Coupling, and only then... which in turn drives the rear wheels. You'd have to stop the front wheels to see if the VC is working and unless you have an LSD you'd have to apply even pressure to the rear wheels too... it's best to take it out and measure the torque required to spin it. The one I have out of the car is probably in the 120-150ft/lbs ...very stiff. (with nice clear fluid inside) I have two god units if anyone needs one by the way. From what I have read it's fairly easy to take it out if you only remove the transfer case right cover. From looking at mine, they are really, really well made and last a very long time IMHO, doubt yours is bad but you never know until you test it ;)
 

tubasteve

New member
gtfour77":b6w0uz2k said:
If you guys look at the diagram, the front wheels(front diff) are working first...then the power gets transmitted to the center diff (open)...once that strats to slip it gets transmitted to the Viscous Coupling, and only then... which in turn drives the rear wheels. You'd have to stop the front wheels to see if the VC is working and unless you have an LSD you'd have to apply even pressure to the rear wheels too... it's best to take it out and measure the torque required to spin it. The one I have out of the car is probably in the 120-150ft/lbs ...very stiff. (with nice clear fluid inside) I have two god units if anyone needs one by the way. From what I have read it's fairly easy to take it out if you only remove the transfer case right cover. From looking at mine, they are really, really well made and last a very long time IMHO, doubt yours is bad but you never know until you test it ;)

not calling you out, just saying how i saws it :p if im wrong dont beat me too hard.

'when there is a difference in speed from the front(main driven wheel[unless wrong]) it causes the vc to heat up the fluid inside causing the power to be added more and more to the rear until 'locked' or they start to have equal speed thus cooling the fluid inside and losening the tight on the rear.'

"if you guys look at the diagram"

did i miss this? :shock: if so help me.

-tubasteve
 

sleeper

New member
gtfour77":3bgbswce said:
If you guys look at the diagram, the front wheels(front diff) are working first...then the power gets transmitted to the center diff (open)...once that strats to slip it gets transmitted to the Viscous Coupling, and only then... which in turn drives the rear wheels. You'd have to stop the front wheels to see if the VC is working and unless you have an LSD you'd have to apply even pressure to the rear wheels too... it's best to take it out and measure the torque required to spin it. The one I have out of the car is probably in the 120-150ft/lbs ...very stiff. (with nice clear fluid inside) I have two god units if anyone needs one by the way. From what I have read it's fairly easy to take it out if you only remove the transfer case right cover. From looking at mine, they are really, really well made and last a very long time IMHO, doubt yours is bad but you never know until you test it ;)


You should make a guide on how to take this item out in a fast\easy way..

Did you do any work on it? or is this the stock spec?
 

gtfour77

New member
tubasteve":1r4vnawp said:
gtfour77":1r4vnawp said:
If you guys look at the diagram, the front wheels(front diff) are working first...then the power gets transmitted to the center diff (open)...once that strats to slip it gets transmitted to the Viscous Coupling, and only then... which in turn drives the rear wheels. You'd have to stop the front wheels to see if the VC is working and unless you have an LSD you'd have to apply even pressure to the rear wheels too... it's best to take it out and measure the torque required to spin it. The one I have out of the car is probably in the 120-150ft/lbs ...very stiff. (with nice clear fluid inside) I have two god units if anyone needs one by the way. From what I have read it's fairly easy to take it out if you only remove the transfer case right cover. From looking at mine, they are really, really well made and last a very long time IMHO, doubt yours is bad but you never know until you test it ;)

not calling you out, just saying how i saws it :p if im wrong dont beat me too hard.

'when there is a difference in speed from the front(main driven wheel[unless wrong]) it causes the vc to heat up the fluid inside causing the power to be added more and more to the rear until 'locked' or they start to have equal speed thus cooling the fluid inside and losening the tight on the rear.'

"if you guys look at the diagram"

did i miss this? :shock: if so help me.

-tubasteve

Nevermind, you are right...I have not looked at the diagram for a while(I must be getting old, it's only been two months since I did all the research!) and thought the front diff "worked" first. It's actually the center diff that is driven directly by the output shaft splitting the output force between the frond diff and the rear transfer..... I need to leave and go live in my simple one-diff trans MR2 world...heh Either way, I am still a believer of diff and coupling testing off the car.
 

gtfour77

New member
sleeper":36bywafj said:
gtfour77":36bywafj said:
If you guys look at the diagram, the front wheels(front diff) are working first...then the power gets transmitted to the center diff (open)...once that strats to slip it gets transmitted to the Viscous Coupling, and only then... which in turn drives the rear wheels. You'd have to stop the front wheels to see if the VC is working and unless you have an LSD you'd have to apply even pressure to the rear wheels too... it's best to take it out and measure the torque required to spin it. The one I have out of the car is probably in the 120-150ft/lbs ...very stiff. (with nice clear fluid inside) I have two god units if anyone needs one by the way. From what I have read it's fairly easy to take it out if you only remove the transfer case right cover. From looking at mine, they are really, really well made and last a very long time IMHO, doubt yours is bad but you never know until you test it ;)


You should make a guide on how to take this item out in a fast\easy way..

Did you do any work on it? or is this the stock spec?

I have a spare transfer case but I am really not going to have the time to do a write up... This is all stock spec. I think mario did it on the car, might want to PM him possibly.
 

sleeper

New member
Or do you have a picture of how they have done it? Where they machined it and where they put the filler hole?
 

lalojamesliz

New member
^? I just saw this thread and now I'm interested myself :) I have a st205 trans sitting in my garage just waiting to be installed and I would like to make a drain and fill hole to replace the fluid. Did anyone confirm what fluid is inside?
 
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