Vanagon – syncro viscous coupling anatomy – part 1

This post is just to clarify, a little, how the plates inside a viscous coupling (VC) are arranged. My post on replacing a VC shows more pictures of the assembly and the seals.

Maybe a couple of pics of the VC (end plate removed) to set the scene. Note the end shims, and the absence of the circlip (groove for it in shaft is visible) that keeps the plates all together.

Another angle, end shims removed.


There are 24 pairs of plates in the VC. One set are keyed to drive (or be driven by, semantics) the VC housing itself. So these plates have notches around the edge that fit in internal splines on the VC housing. They also are the plates with the circular holes in them. The other set of plates, slightly smaller in diameter, are keyed to drive the central splined shaft. They have slots in them. The propshaft from the transmission is connected to the housing, the pinion of the front differential is connected to the central shaft of the VC. The silicone fluid filling the VC is what mediates the power transfer between the plates. I won’t be going into the silicone fluid in this post.

There are spacers between pairs of plates, and these spacers fit into the hole in the middle of the plate that is keyed to the housing. The spacer is (all measurements are approximate) 0.065″ thick. The plates themselves are 0.040″ thick. So with the spacer partially lying in the hole of one plate, it only projects about 0.025″. That means the plate pairs are separated from each other by 0.025″. I think it is time for a simple diagram.

Does that diagram make sense to you? You can make out the spaces between the plate pairs in this picture of the entire stack o’ plates out of the housing but still on the shaft.

Oops, looks like I left the last plate in the housing. Also the aluminium ring I am using to support the plates is causing the plates at the end to be pushed upwards. Of course when in the housing they are all aligned. Here is a closer view, no mistaking the pairing of the plates.


And here is a stack of 2 pairs, plus one shaft keyed plate on top.

I think I have established that the plates are in pairs 🙂

I’ll post pictures of the wear patterns on the plates and try and relate that to the pairing of the plates in the next part. All comments and corrections welcome.




  1. #1 by Ed on November 21, 2011 - 11:00 pm

    very interesting!

  2. #2 by Peter on November 22, 2011 - 5:13 am

    Bloody marvelous – thanx Alistair

  3. #3 by Idahodoug on November 22, 2011 - 8:21 am

    Fantastic! Clear as a Bell! 🙂 Doug

    • #4 by albell on November 22, 2011 - 8:41 am

      If you meant that as a pun, then I take it as “clear as mud” 🙂


  4. #5 by Mark de Visser on November 22, 2011 - 1:06 pm

    Hello Alister,

    Nice job on the Visco
    Smelly stuff the silicone oil of the Visco or looked it normal due to leakage?

    Here some links about some germand who does there overhaul them selves and put it on youtube.

    Here a price list whe i did my visco with a torqu test report

    Click to access preisliste2_e.pdf

    here wher we can buy seals and oil in Germany

    Keep on going and enjoy the way of syncro live
    I will be reading your blog it was very helpfull to me

    kind regards


    • #6 by albell on November 24, 2011 - 12:15 pm

      Thanks Mark,

      I’ll try and collate all of the good VC links into one post… someday 🙂



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: