I have a 2105 F56 S (100k miles), and upgraded the clutch and put in a limited slip diff. Finally buttoned it up last night, and tried to test the new clutch. Started getting a noise/vibration in 1st gear and reverse. Granted it isn't all the time, but almost stalls the car. After test drive could smell the clutch as well.

Have done:
1. installed new clutch, flywheel, pressure plate and throw out bearing/fork. torqued the pressure plate at 20 ft-lbs. (made sure the clutch disk had the sticker "toward gearbox" facing trans)
2. put everything back together and test drove; noticed 1st and reverse gears want to stall out, and could smell clutch after short test drive (less than 4 miles)
3. researched what could be causing; pressure plate too tight; multiple articles about bleeding slave cylinder
4. bleed slave cylinder using Motive power bleeder @ 13psi, 2nd bleeding ended w/ mass quantities of air;
5. pull out slave cylinder, don't see any visible fluid leaks, but the air during bleeding makes me think it is bad.

My question would be, would a bad/failing slave cylinder cause the clutch issue I'm experiencing, or did I somehow create 2 new problems?

 

Here is what JMTC Performance says when replacing a clutch

"JMTC recommends ordering one of our installation kits and a new master clutch cylinder. The master clutch cylinder has a check valve that can become blocked and will keep the system pressurized and partially or fully engaged. If it is blocked it will impede performance and can and WILL shorten the life of the clutch due to slippage and/or full engagement of the throw-out bearing.

If the check valve is blocked the clutch could slip right after installation and the peddle/pressure plate fingers may bind when the clutch peddle is depressed. If the master clutch cylinder check valve is blocked you will be lucky if the clutch lasts 15 to 20k miles Kevlar or not! Our full Install kits are insurance that your clutch install will go well, the clutch pack last long, and prevent unnecessary premature failure."

Source

 

Pulled it all apart and double checked everything. Did find that I might not of torqued the pressure plate enough, but still no major sign of anything wrong. Put it all back together, and installed a new slave cylinder for added measure. The old slave cylinder had 100K miles and the boot was falling apart, plus I've had the master cylinder replaced about 1K miles ago (so don't think it is the master). The clutch is still pretty grabby in 1st and reverse, but figure I need to bed it in and that I'm now using a single mass flywheel vs the dual mass. I've also noticed if I am quicker off the clutch pedal, I don't feel the vibration/grabbiness (sp). After driving I'm not smelling a clutch burning smell, and it will get up and go. Went to get some gas and ended barking the tires pulling out (without trying).