German transaxle rebuilt viscous coupling

[SyncroChrick]

I just want to add that the TheSamba crowd is the best. Thanks for helping.

[MarkWard]

Probably unrelated, but it looks like the driveshaft is installed backwards from the one picture you posted.
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[tencentlife]

[Sodo]

Alaskadan, the VC cannot be related to any issues driving straight (not turning etc) while F+R wheels have appx same traction (all rolling same).

[crazyvwvanman]

What are there about 25 possible combinations front and rear?
20 of them are bad for the VC?

That is just with stock VW r&p possibilities.

Mark

[vandoka]

Mark, I did get to try your test. With the driver's side lifted and tires marked with tape the rear tire rotated adout 10-15%faster than the front tire. I also tried tencent life's suggestion. Turning the front wheel with all others on the ground did have some resistance but I did not have a torque wrench to measure, it felt close ton20-30 lbs torque. So I guess this clarifies that the viscous coupling is ok?

[crazyvwvanman]

Yes, VC probably fine but you have a big problem. The r&p gear set in the front doesn't match the back. You may be able to simply read the codes stamped into the tranny and front diff housings to look up and see what they each came with when made. That of course assumes they still contain the gear ratios they each came with.

With some careful time you can do a test to figure out what ratio is in each end of your Syncro.

With both wheels on one side lifted, mark the center driveshaft and one tire. Turn that tire some number of exact turns, like 5. Carefully count how many full rotations the driveshaft makes during that time. It has to be precisely done. Write it down including an estimate of fraction of turn at the end.

Then repeat for the other wheel on the same side to get the ratio for that end.

As to your 10-15 %, about 11% would be right for a 4.86 rear and 5.43 front, the most likely mismatch as they are the most common ones.

Mark

[vandoka]

Thanks for all the good info. and possible fix to my dilemma. I will continue to investigate the gear ratios and see what I find. Turns out I dropped the driveshaft and drove it home no problems other than a bit of vibration and noise. And yes, after consulting bentley the driveshaft had been installed backwards....will make sure to fix that when it goes back in. Who knows what other secrets this ol' Doka has in store

[vandoka]

Crazyvwvanman,

I thought I would fill you in on the ratios I found for my doka. It is a diesel from sweden and the only numbers I found on the trans were on the passenger side, 09 301103, I also found the code on the front diff, 6nd, which I think is the 5.43 ratio.

After trying the tire 5 times and counting revolutions of the drive flanges I got the following:

front 5: 13.6 revolutions

rear 5: 12.15 revolutions

so how does this calculate into the trans gear ratio if you don't mind?

Thanks.

[Sodo]

12.15/13.6x5.43=4.86
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[Howesight]

"After trying the tire 5 times and counting revolutions of the drive flanges I got the following:"

front 5: 13.6 revolutions: THIS IS A 5.44 RATIO (by the arithmetic, that is, the difference likely being caused by a slight measurement error meaning the 5.43 ratio is what you have)

rear 5: 12.15 revolutions" THIS IS A 4.86 RATIO

Your arithmetic is complicated by the fact that when one wheel is stationary, and the other is rotated, the diff causes the wheel to rotate twice as fast as would be the case if both wheels (on one axle) turned the same speed.

Therefore, you correct by either doubling the pinion shaft revolutions or halving the wheel rotations to solve for the gear ratio.

Illustration 1:
(13.6 + 13.6) = 27.2

27.2/5 = 5.44

Illustration 2:

(12.15 + 12.15) = 24.30

24.3/5 = 4.86
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'86 Syncro Westy SVX

[Howesight]

[Sodo]

I’m walking around at a farmers market. I haven’t had time to think about it but the numbers looked pretty good .
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[crazyvwvanman]

This explains why the center driveshaft was "reversed" from "normal" since VW put the shaft end with the guibo to the front on diesels. So it wasn't backwards after all. Don't know why VW did this but I'm sure they had a reason.

Mark

[Sodo]

[Howesight]

Sodo:

You are absolutely right. I read your post too quickly and did not notice you multiplying the fraction by 5.43. My apologies.
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'86 Syncro Westy SVX