Porsche 964 C4 Longitudinal Slave Cylinder Rebuild

Took some time last weekend to repair the leaking longitudinal slave cylinder on Valerie’s 964. It has had a slow leak for awhile now, occasionally the 4wd light would come on when driving, so it was time to tackle it. Parts have been here for awhile, just no time. The Longitudinal slave cylinder controls the amount of power to the front wheels from the transmission. They are quite expensive, but ninemeister IIRC, has finally sourced the seals to rebuild the unit, rather than replace it.

Mounted on the nose of the transmission, it isn’t too much work to get it off.

A circlip holds the unit together.

And removed. Once that is out, you can tap the cylinder to get the guts out. Hard to see, but there is actually a piece of seal laying in the cup.

And where the piece came from.

Cylinder in good shape with no pitting.

The instructions show how the seals will go together. They are a real pain to get back on the cylinder

Old seals removed.

And new seals going on. The end seals simply wrap around the cylinder, which makes it a little hard to get back in the housing as they want to spring open.

And back up in the car.

I also replaced the line while in there. They are cheap and the ends will seize over time, so a good time to replace it. After that, bleed the system with a vacuum bleeder and the computer, and it should be good to go. The kit also includes seals for the lateral slave cylinder as well, but that was replaced by the previous owner not too long ago.

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One Comment

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Flavien Sicre

October 12, 2015 at 1:47 PM

Very interesting ! I am encountering the same issues as you had, with the transmission light on … Can you tell me how to buy the seals ? Thank you !

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