Question about Clutch

[Porsche_Monkey_4life]

I have 3.4 conversion on my 986. The conversion was done by the previous owner. Aside from the engine he did many other other upgrades ie hid kit hr coilovers etc....Among these upgrades was what I was told to be a lightened flywheel and sports clutch. My question is: if this is the case how can I tell ? I was told that lightened fly wheels make an oscillating rasping noise when the clutch is not engaged and the car is in neutral, which my car does. Also I believe my clutch is starting to give out because it slips but only under heavy load. Under normal driving it engages fine. Is that common? My last question is, if I indeed have a lightened flywheel, do I need a special clutch, also am i shopping for a 911 clutch or a boxster clutch?

[Bill_SoCal]

El Paso? I was just there last week for business (El Paso/Juarez). I haven’t seen many Porsche’s driving through town. Do you have a dealer or reliable service center there? I like the area…as a matter of fact, I’m there often.

There are many more qualified people to answer your question than me, however, I do have experience with lightened flywheels from my college days and my high performance VW engine. At that time I had the flywheel lightened to 10.5 pounds and balanced. I also had a 200mm ceramic clutch installed to grab the flywheel (with a heavy duty pressure plate). In addition, I had the crankshaft and flywheel match-drilled from 4 dowels to eight dowels so that the crankshaft would not become oval at the dowel pin area from the torque. So here’s what I do remember, the lightened flywheel allowed the engine to rev on a dime. It was all about getting the jump for the short distance. I went to a ceramic clutch to keep from burning the standard clutch (went through several). I do not recall an oscillating rasping noise from the lightened flywheel. I was running straight cut gears back then (camshaft), so my 2276 with dual 48 IDA’s sounded loud and commanding…and the whining came from the gears and not the flywheel.

You can’t tell if the flywheel has been lightened unless you physically look at it (unless you have the paperwork from the machine shop or mechanic). If the clutch slips it must be replaced. There is not an option there. If your flywheel is fact lightened, you might consider getting a standard flywheel installed unless you’re running the ¼ mile with a ceramic clutch. I personally am not aware of any reason a daily driver would have a lightened flywheel. As a matter of fact, that makes for uncomfortable freeway driving (not smooth). If you decide you want to keep the lightened flywheel, you’ll need to get a clutch that will engage and not burn out. I will tell you driving with a ceramic clutch is not comfortable at all. It’s either engaged or not engaged…again, it’s been about 25-years since I’ve messed with a lightened flywheel. You’ll be shopping for a Boxster clutch and heavy duty pressure plated for your Boxster and not a 911 clutch assembly.

If it was me, I would buy a new flywheel, clutch, and pressure plate assembly (stock). I drive my Boxster like I stole it and I have 152,300 miles on the original clutch as of my arrival to the office this morning.

Messing with Boxster clutch assemblies is not so easy…in my VW days, it was simply unhooking the electrical, putting a screw in the fuel line, and undoing the four (4) 17mm bolts from the transaxle and dropping the engine onto a skateboard. Now those were the days!

Hope this helps.

Bill :beer:

[Porsche_Monkey_4life]

El Paso? I was just there last week for business (El Paso/Juarez). I haven’t seen many Porsche’s driving through town. Do you have a dealer or reliable service center there? I like the area…as a matter of fact, I’m there often.

There are many more qualified people to answer your question than me, however, I do have experience with lightened flywheels from my college days and my high performance VW engine. At that time I had the flywheel lightened to 10.5 pounds and balanced. I also had a 200mm ceramic clutch installed to grab the flywheel (with a heavy duty pressure plate). In addition, I had the crankshaft and flywheel match-drilled from 4 dowels to eight dowels so that the crankshaft would not become oval at the dowel pin area from the torque. So here’s what I do remember, the lightened flywheel allowed the engine to rev on a dime. It was all about getting the jump for the short distance. I went to a ceramic clutch to keep from burning the standard clutch (went through several). I do not recall an oscillating rasping noise from the lightened flywheel. I was running straight cut gears back then (camshaft), so my 2276 with dual 48 IDA’s sounded loud and commanding…and the whining came from the gears and not the flywheel.

You can’t tell if the flywheel has been lightened unless you physically look at it (unless you have the paperwork from the machine shop or mechanic). If the clutch slips it must be replaced. There is not an option there. If your flywheel is fact lightened, you might consider getting a standard flywheel installed unless you’re running the ¼ mile with a ceramic clutch. I personally am not aware of any reason a daily driver would have a lightened flywheel. As a matter of fact, that makes for uncomfortable freeway driving (not smooth). If you decide you want to keep the lightened flywheel, you’ll need to get a clutch that will engage and not burn out. I will tell you driving with a ceramic clutch is not comfortable at all. It’s either engaged or not engaged…again, it’s been about 25-years since I’ve messed with a lightened flywheel. You’ll be shopping for a Boxster clutch and heavy duty pressure plated for your Boxster and not a 911 clutch assembly.

If it was me, I would buy a new flywheel, clutch, and pressure plate assembly (stock). I drive my Boxster like I stole it and I have 152,300 miles on the original clutch as of my arrival to the office this morning.

Messing with Boxster clutch assemblies is not so easy…in my VW days, it was simply unhooking the electrical, putting a screw in the fuel line, and undoing the four (4) 17mm bolts from the transaxle and dropping the engine onto a skateboard. Now those were the days!

Hope this helps.

Bill :beer:

Thanks Bill I appreciate the info. I was thinking the same thing. To add to the sports clutch and lightened flywheel theory I had the clutch as you put it is uncomfortable, it's either engaged or not, impossible to drive smoothly. I'll be looking out for a stock assembly. Anyone have any suggestions as for where to shop for one? Also what should labor on that be?

[phillipj]

Have to agree about the light flywheel. I had one in my last 996 and now I have the 997 with the stock DM flywheel. It's so much better and easier to drive on the street.

Although the LWFW is a bit quicker it's not a good trade off.

If you want to stick with the LWFW the you should get a sprung clutch. Look at the SPEC products. You should get a new TO bearing, pilot bearing as well as new flywheel bolts. You can also get the 997 fork (just a few bucks.) You will never get rid of the rattle. That is just the nature of the beast. Listen to a new GT3 and you will hear the same sound.

Good luck

Edited September 16, 2009 by phillipj