Clutch Cylinders - master & slave

Discuss with fans and owners of the most luxurious aircooled sedan/wagon that VW ever made, the VW 411/412. Official forum of Tom's Type 4 Corner.
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gearheadgreg
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Clutch Cylinders - master & slave

Post by gearheadgreg » Thu May 10, 2018 9:36 am

OK, so the slave cylinder on my 412 is weak. I understand that the slave cyl's are basically unobtanium now, and have read Ray's (excellent) posts about the type of seal material, size, etc. to make new seals.

I'm sure I could find a seal that would work, possibly needing to modify the piston, or make a new one. However, I have another question -

Why does the 412 need such a huge slave cylinder? I understand the relationship of leverage ratios between the master and slave, but I'm wondering if we can swap in a different (Vanagon for example) Master AND slave cylinder. If the earlier cars used a 19mm slave, with a different master, I"m sure, I wonder if the clutch arm doesn't need a huge push on it.

I'd love to find a more universal solution for all the 412s out there, either Vanagon, or something universal, or adapted from a much more common car.
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raygreenwood
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Re: Clutch Cylinders - master & slave

Post by raygreenwood » Sat Jun 02, 2018 3:35 pm

Sorry it took me song long to get back to this. You got the answer right!.....the 411/412 was supposed to be a "luxury"-esque car. They made the slave cylinder huge so it would have a feather light clutch action. I actually think its too light. I would like to have some more snap in it.

The earlier 411's had a 22mm or 25mm slave cylinder bore (going off memory). I have never driven one of those but by design/math the clutch action should be double the effort of the later 44mm slaves.

Yes...actually you can use anything that you can fit that has the right piston stroke length. This is critical.....because having excessive slave stroke length will WRECK the clutch throwout fork...by grinding its pivot point against the fingers on the pressure plate. Those clutch forks do not grow on trees!

One very good possibility is the late model slave cylinder from a Jetta or Golf. The bolt pattern is similar...the stroke length could probably adjusted by a spacer between the slave and bell housing. I am betting that even if the bolt pattern is slightly too wide or narrow...that can be accommodated by the spacer plate as well.

Right here in this link you see a Jetta/Golf Mk6 slave cylinder. The form should ring a bell....two bolt pattern
https://www.fcpeuro.com/products/audi-v ... cgEALw_wcB

This one is from a Mk3 VR-6 engined Jetta
https://www.autohausaz.com/pn/357721261 ... hKEALw_wcB

There are some from the Mk4's that are similar. A lot of the watercooled VW and Audi slave cylinders from about 2000 and on are two bolt. There are numerous configurations...many of them could be made to work easily.

As for the master cylinder...tear it down NOW. If the bore is not pitted and the pistons have no serious corrosion...you can rebuild it with seals and brass flap valves from any Vanagon master cylinder kit or from any 19mm brake master cylinder kit.

At some point toward the end of this summer I will be doing a re-plating run for 411/412 clutch and brake master cylinders. I have a pile of cores....and will be honing them smooth and replating back to factory size with electroless nickel. As long as you never scratch the bore they will never rust again. In this way if you simply put in new seals every few years...they will last forever. Ray

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