Hello all!

I recently replaced the clutch and installed a single mass flywheel conversion kit. When replacing the clutch, I also replaced the guide sleeve, fork bushings and seals.
The car feels great, clutch is way higher compared to my old one, but I’m having an issue. When I turn the A/C on, at idle I can hear a rattle that would go away when I depressed the clutch.

I’ve read a lot about that kind of rattle, and people claim that it’s a single mass flywheel common behavior. I ruled out TO bearing, belt tensioner, supercharger and alternator pulley seem to be in good condition. I’m not sure how to check the A/C compressor when engaged. Crank pulley also seems in good condition although I want to install a liquid filled one, but because of my teacher salary I need to wait a bit longer for that one.

When I first start the car in the morning the sound disappears (I guess because RPMs are higher at that moment), but even after starting the car, if I turn the A/C on, the rattle will begin.

After the car has warmed up with the A/C off is way less, but I’ve been noticing that when the weather gets hotter, the rattle gets worse. (I live in Florida, so it’s way too hot).
Not sure if maybe since here never gets cold, changing from Redline MTL to Redline MT-90 would help with the rattle.

Any advice you can provide would be greatly appreciated.

 

It's gear chatter in the transmission, and I believe it's pretty normal for single mass setups - and especially for lightweight flywheel setups. Which kit did you put on? I have the same noise on mine, and it's noticeably worse with the AC on. I suspect it's one of the reasons the OEM setup uses the dual mass flywheel - to better dampen the impulses off the cylinders firing, resulting is less gear rattle in the transmission.

The Valeo single mass conversion is only about 2 lbs. lighter than the OEM setup from memory, but that lower mass to absorb the impulses from the engine, combined with the damping being done by the springs on the clutch disc basically doesn't do quite as refined a job smoothing things out. With the AC on, the engine is working a little harder to turn the compressor and those stronger impulses are rattling the gears.

I've also thought about going with a thicker gear oil like MT-90 to quiet it down a little, but it gets cold enough here that shifts even with the MTL on cold winter days can be hard until the car is warmed up a little. In Florida, you'd probably be okay running the MT-90 year round. When the gear oil is colder and thicker in the fall and winter here, it does seem to be quieter, but the rattling is not completely gone.

I also installed a fluid dampened crank pulley, which helped a little, but mainly only with the AC off.

 

I finally had time to change the gear oil to MT-90 and it really helps reducing gear chatter. In regards to shifting, I feel it less crunchy when changing gears.
It helps with the noise but doesn’t disappear of course, but now it’s something I can live with (or maybe I just got used to it).
Eventually I’ll install the fluid filled crank pulley just to give me peace of mind.

 

Thanks for reporting back - interesting that it feels less crunchy. I may have to give a try in mine the next time around.

I was curious and looked up the OEM fluid and apparently its 75w-80 (MTF 2). MTL is 75w-80, and MT-90 is 75w-90. There's also a MT-85 (75w-85) that Redline offers. At cold temps, all are rated the same at 75W, so they should be pretty similar on cold starts.

For the crank pulley, I think the ATI super damper one gets the most recommendations from what I've seen here. I couldn't use that one since mine is a 6-speed swap on the base engine.

 

I've had two Valeo single-mass clutches in my R53 with none of the noise you're mentioning. The A/C and related compressor have nothing to do with your clutch. If the rattle begins when you turn on the A/C those components are where you need to be looking.