Rebuilt transfer case options with viscous coupling discussion.

[mudkicker715]

I believe the Eaglepaedia has something in there about fluid levels and volumes. But you could google NP128/np129 for that info. But someone here may know as well, I will update this if I find it first.

ok here is the link for the TM, scroll down to the NP 128 is says 3.3 liters (7 pints)

http://www.amceaglenest.com/~iowaeagl/guide/index.php?title=July_1985_-_IS_7E_-_General_Information_and_TSM_Pages_for_the_NP_128_Transfer_Case

That would be magic for a vc to hold that much

[captspillane]

The service manuals don't detail how to rebuild a viscous coupler. Its supposed to be done in a factory. The 3.3 L capacity is for the whole transfer case.

Why bother looking for that amount until we have a source for the silicone fluid? Its special stuff and some degree of toxic. Is there a place to order the Viscous Coupler fluid for a VW or other make?

[Hawk258]

**Shrug** that's what the book said. it called for dex II and 3.3 liters. check the link I assume that would be from completely empty though.

[Hawk258]

Sorry... the 128 does NOT have a VC... it was a bad example I pulled the wrong case info... sorry.

[mudkicker715]

Sounds right for the case. However some cases use other lube such as 10w30

[Hawk258]

ok here is an update and an image of a VC, this may help and it appears that it is possible to get the VC fluid. I assume that it is possible to order the clutches for the vc not sure still flexing my google fu here.

http://www.vanagon.com/syncros/technica/vc-expert-interview/index.htm

[captspillane]

So when in comes to rebuilding the viscous coupling, does anyone know how much fluid is supposed to go in it?

Its the right answer for the wrong question. The question asked was how much viscous silicone oil is contained in the viscous coupler. It should be less than a pint. Its possible that the fluid from a VW viscous coupler is still in production and available to allow someone to rebuild their own viscous coupler. Its the fluid that loses its viscosity over time, the internal parts themselves are not in contact and should not wear out.

To be clear, the viscous coupler is about 4 inches in diameter and about  4 inches long. It is one internal part inside the transfer case.

[Hawk258]

well, It I think the answer is in my previous post, as there is suppose to be room for expansion. but that's just what I understand at the moment

[eaglefreek]

What I have read there needs to be the right combo of oil and air for it to work properly. The gentleman I talked to at RSG said he used to get 5 gal buckets of the oil from Dupont. No idea what it is or if it is still available.

[Hawk258]

What I have read there needs to be the right combo of oil and air for it to work properly. The gentleman I talked to at RSG said he used to get 5 gal buckets of the oil from Dupont. No idea what it is or if it is still available.

yes I have found some from the manufacturer but they link you to a local distributer, I will post the like for you folks that are interested.

http://www.dowcorning.com/applications/search/products/details.aspx?prod=02967642&type=PROD

[carnuck]

I believe the Eaglepaedia has something in there about fluid levels and volumes. But you could google NP128/np129 for that info. But someone here may know as well, I will update this if I find it first.

ok here is the link for the TM, scroll down to the NP 128 is says 3.3 liters (7 pints)

http://www.amceaglenest.com/~iowaeagl/guide/index.php?title=July_1985_-_IS_7E_-_General_Information_and_TSM_Pages_for_the_NP_128_Transfer_Case

Except the NP128 has no viscous coupler. That's the tcase lube oil they are talking about it.

[carnuck]

So when in comes to rebuilding the viscous coupling, does anyone know how much fluid is supposed to go in it?

Its the right answer for the wrong question. The question asked was how much viscous silicone oil is contained in the viscous coupler. It should be less than a pint. Its possible that the fluid from a VW viscous coupler is still in production and available to allow someone to rebuild their own viscous coupler. Its the fluid that loses its viscosity over time, the internal parts themselves are not in contact and should not wear out.

To be clear, the viscous coupler is about 4 inches in diameter and about  4 inches long. It is one internal part inside the transfer case.

In FSJs, the coupler tears apart and the silicone fluid eats up the bearings like liquid sand.

[Hawk258]

Sorry... the 128 does NOT have a VC... it was a bad example I pulled the wrong case info... sorry.

yeah, I updated that, again I apologize for that.

[Jurjen]

Here is the original GKN patent:

http://worldwide.espacenet.com/publicationDetails/originalDocument?CC=US&NR=4022084A&KC=A&FT=D&date=19770510&DB=EPODOC&locale=nl_NL

It makes interesting reading.

The GKN people knew that it worked, but did not know why ....

The original silicone oil also came from Dow Corning ....

Some statements about filling in it too.
The coupler starts really doing something once 100% fill rate is reached due to thermal expansion. So fill it 100% and don't close it. Warm it up to 212F and the excess goop will flow out. Then close the coupler. Now you know that you have a coupler that starts working from 212F. Easy peasy.

Roy Lunn must have done the same experiments and came to a 70% fill rate.

I would do it like this:
Clean the internals with white spirit.
Then fill it to the brim with white spirit.
Empty it in a glass measuring cup (from the kitchen) and make a note of the level.
Use the same cup and fill it with silicone oil 70% of the previous measurement and put that in the viscous coupler.
Why not use the silicone oil to do the measurement? It is too goopy, it won't come out again.
So better use something nice and thin like white spirit.

[carnuck]

Found out the S10 axles are 5/16" longer fully compressed.