Project: 2003 BMW M3

[Jake]

I always thought master/slave cylinders were an on/off thing (either they work or they don't), not something that could necessarily affect shifting? Do you know what fluid is in the transmission?

If the seals on one or both are starting to fail, you may still have the ability to disengage the clutch, but not 100%, due to lack of pressure to push the assembly fully apart. Sometimes pumping the clutch pedal twice will help with that although obviously at that point, you'd want to replace the offending part.

Seems like the BMW stuff usually leaks a bit before it just goes out - the Miata slave was the exact opposite. One day of pretty high shift/clutch effort and then I had nothing.