My viscous coupler rebuild

[tim_ha]

After I recently found that my viscous coupler and input shaft splines were completely stripped, I bought a used front differential. Upon inspection of the used diff, I decided to pull the VC and input shaft and use them in my much cleaner diff. Not knowing the state of the VC, I decided that the experiment of rebuilding the VC myself was worth my time and effort. Here, I will try to document the process.

First, I used the stripped VC as a trial run for disassembly and cleaning. I found that after removing the big circlip, the lid was tough to remove. By backing the fill/inspection port bolts out a bit and using a big flat head, the lid can be pried out quite easily.

Opening it up, I discovered some very dark fluid.

I then set it on a tupperware container for a couple days to drain.

Then, out came the circlip on the inner shaft that holds all of the discs in place.

Both end discs (top and bottom) are the hole type discs. They have two small additional holes and a larger diameter inner hole than the others. They are not held in by the circlip but are free to float.

There are three thin spacers between the circlip and the first slotted disc.

Then begins the trios of one slotted disc, one spacer, and one holed disc. I decided not to use any solvent to clean, but simply wiped off each disc and inspected as I went. I found it easy to feel the "burred" side and smooth side of the discs. The slotted discs all have a small circular mark on the smooth side which indicates the top of the disc for installation. The holed discs did not have any orientation, some were burred side up, others were smooth side up.

I did not clock the discs as I removed them, but did notice that consecutive slotted discs did not line up. I did keep the order and top/bottom orientation the same by cleaning and re-stacking as I went.

I did note some contamination of the fluid seemed to be present. There was a dark substance that seemed to be suspended in the fluid and also some greenish fluid, probably oil, that sat on top. My guess is that the dark suspended contaminant is tiny metal chunks. They even seem somewhat magnetized, making cool patterns.

More to come...
_________________
1986 Syncro Sunroof EJ22
www.subagonsouth.com

[insyncro]

Nice pictorial.
Curious to see it turns out.

[kryptkat]

Thanks Tim for the informative trend. Looking forward to your next update.

[rubbachicken]

very interesting, don't be shy with the pictures

_________________
lucy our westy

lucy's BIG adventure

meet 'burni'

[Volkska]

ITs one thing to research and read, but seeing the pictures really helps my understanding of everything, thank you! I'm guessing the dark liquid is that silicone blend?

[Christopher Schimke]

Yes, looking forward to more!

For some reason, this thread reminded me of this -


Link

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[tim_ha]

[Christopher Schimke]

[LandSailor]

That's neat. I've always wondered exactly what was inside them.

[tim_ha]

Opening up the VC that I will be rebuilding, I found not much fluid and the same dirty sludge that was in the diff oil.

The discs in this one showed lots of wear. The nice tan colored nickel plating (I think that I read that is what it is) was often discolored or worn off.

Some discs showed signs of sitting in a stack of the same type disc with some sort of discoloration from adjacent discs.

Once I got all of the discs out, I found the culprit for the lack of fluid and amount of sludge... A twisted seal ring. This guy allowed silicone fluid to leak out and nasty dirt from inside the diff to get in. If I had to take a guess, this VC failed to the transfer no power state rather than the more common too aggressive state.

There was also evidence of certain pairs of discs being a bit more sticky causing a deeper wear groove in the center shaft.

With the terrible state of these discs, I decided to use the discs from the much cleaner, stripped VC. This is probably a big no-no to mix and match parts like this, but I inspected everything to make sure they were the same dimensions etc, and decided to go for it.

I was able to get a VC rebuild kit form a Samba member, selling me his last set of seals that he sourced from Europe as well as the refill fluid that he got from an unknown (to me) company on the East Coast. The fluid was reported to have 30,000mPas viscosity which is reported to be the same as OEM.

With all of the discs cleaned as well as all of the sludge cleaned out of the VC internals, it was time for the exciting part... The refill.

First, I installed the new seals making sure to lube them up with a bit of the new silicone oil. Then, I installed the center shaft into the outer housing making sure that the seal did not get twisted in the process.

I decided to do as the Germans did in the rebuild videos that are out there and use the subtraction method for filling the VC with fluid. I weighed the fluid, container, and a popsicle stick to assist in pouring the fluid. From this weight I subtracted the weight of fluid that I wanted to fill to get a final target weight. The factory fill spec is reported to be 278g of fluid, and I wanted to err on the side of a slightly aggressive VC, so I decided to put in 279g.

From the 340.9g original weight, minus 279g fill weight, the target weight after filling would be 61.9g. I poured in most of the fluid and reweighed, sneaking up on the target weight until it was perfect (some luck on hitting it right on).

It is hard to see the nice clean, clear fluid, but here is the VC housing with 279g of silicone oil in it.

Now, it was time to put the discs in. I had stacked the discs upside-down so that it was just a matter of grabbing one, flipping it and putting it in. I made sure to offset the slots in the slotted discs as I was doing this. After putting about 3/4 of the discs in, I had to push them down and even tried to rotate the inner and out pieces to help the discs settle in the fluid. This took a while. With two discs left, I took a break to eat dinner and when I came back, I was able to get the last two in, add the spacers and the circlip.

With that, it was time for the lid. The position of the lid is important to the balance of the overall unit, and is marked by a divot in the top of the outer case. The ridge on the lid that goes in the break of the circlip should lineup with this divot.

The lid took some persuading to push down all of the way and all I could do was cross my fingers and hope that the seals were still seated correctly.

With that done, I put the VC back in the front diff, making sure to add the spacer on top of it, sealed the diff back up and filled with 1.6qt of Redline.

To test the VC, I had left my rear axles out after rebuilding the CVs. With the rear axles out, I did some preliminary testing as seen in the video below. This was a cold, late night, and I will try to do some more tests before replacing the rear axles. Any thoughts on testing I should do?

As can be seen in the video, preliminary testing indicates a fairly aggressive VC. Only very slow spinning of the rear wheels would be allowed before the front wheels pull the van over the 2x4s. This is a good result for me as I planned to add a decoupler anyway. My hope is that it is not too aggressive to drive coupled in the mixed dry/snowy conditions that we get a lot of here in Colorado.

Link

_________________
1986 Syncro Sunroof EJ22
www.subagonsouth.com

[MarkWard]

Thanks for sharing. I don't suppose there were dimensions in the two lip seals that you got? They might could be matched up at a bearing supply house. The O ring would be easier to solve I think as long as the fluid is available. thanks again

[ragnarhairybreeks]

Great work!

I got stalled on my vc rebuild due to supply line problems on the silicone fluid


I found the same twisted seal. I read that others have found the same thing so it might be a case of excessive pressure forcing the seal to distort.

Alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[gears]

Yes .. or an assembly line or even design dimension error. Either way, it certainly seems to be a common denominator.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[zeohsix]

Has anyone measured the VC seal dimensions? I can tell you the Syncro front wheel seals are 65mm shaft X 80mm housing bore X 8mm width using those figures will get you way more alternatives than trying to look up the application on an auto parts supply Web site. Shaft diameter X Hosing bore X width dimensions would be much appreciated by others if you have one to measure. Thanks! Eric B.

[photogdave]

[ragnarhairybreeks]

I'm sure I did reply Dave, but no problem. It's not like I have nothing to do these days

If you ever take another trip over to the island we can meet up and do the deal.


Cheers


Alistair
_________________
'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[insyncro]

What is the consensus for why this VC turned out aggressive?

Curious to hear thoughts on this.

[tim_ha]

I am curious about what peoples thoughts are on the aggressiveness as well. I also need to do more testing. The only test I performed so far, was with the VC cold, about 38 degrees that evening, and I think that the cold fluid temperature could have a large impact on how aggressive the VC acts. I am thinking that I could go for a short drive, repeat the test, another short drive... and so on. Slowly warming up the VC and repeating the test. Very unscientific, but without a nice bench test setup, it is the best I can do.
_________________
1986 Syncro Sunroof EJ22
www.subagonsouth.com

[tim_ha]

[insyncro]

You have done an exemplary job thus far.
There really isn't a cost effective scientific approach IMHO.

Some will dispute this, but the temperature has an effect on the transmission of power forward.

Check out Derek and Seth Drew's African Adventure testing VCs.
I will link the Vimeo from my computer next chance I get.