Need help with dual mass flywheel...
 

So I had a new clutch & flywheel installed (sachs). The flywheel makes a loud whining sound every time I shift & let out the clutch. Also, makes a lot of nosie when decelerating. Also has a vibration around 3,000 RPM.

Mechanic seems to think its normal. Its been 10 years since I've owned a 986, but I don't remember it making all this noise.

Who installed the clutch and DMS? That's not normal to hear the noise you described. Could it be some of the springs on the DMS have come off or broken. There should be no vibration. When you shut down the engine with the clutch out, do you hear any noise, such as a rattle. If you do hear a noise try shutting down the engine with the clutch depressed. Report back!

For perspective, it would be good to know the background of the mechanic to help understand the "it's normal" response. If it's "some guy with tools" it begins to make sense, if it's a Porsche master mechanic, then I'm really confused.

For the record (and without additional info), I'm in the "not normal" camp, but if the individual falls in to the latter of the two groups, I withhold the right to amend my opinion. Lol.

This is a well respected INDY shop that specializes in German cars and has been in business over 30 years.

You're sure it's a dual mass flywheel and not a lightweight flywheel?
Definitely not normal at all for a good dual mass flywheel.

The vibration could be your motor mount too. Very common, and perhaps your old dead clutch was masking it. Depending on year, if your motor mount is original stock, I’m 100% sure it would be dead and need replacing.

It's definitely a dual mass fly wheel. They were suppose to check the motor mounts as well.

Jim in SC says: The flywheel makes a loud whining sound every time I shift & let out the clutch. Also, makes a lot of noise when decelerating. Also has a vibration around 3,000 RPM.

It's my understanding all this started after the work was done. There was no mention of any vibration prior.

There was a vibration/whining prior to the clutch install. It is better now but still there.

Jake Raby says to avoid driving at a steady 3,000 rpm as that is the worst rpm for engine vibrations in these engines. Having said that, I find that 3,000 rpm in 6th gear is about where my car runs on highways to go with the flow of traffic so I do it all the time. Maybe your old dual mass flywheel was out of spec enough to mask issues that are starting in your motor mount and possibly also your transmission mounts. Or maybe some nuts and bolts weren’t fully torqued on reassembly? Even experts have occasional oversights on basic stuff, and putting it on a lift and taking a look is something I think they would do after you just paid for that big job.

I am not an expert in these matters by any means but these things may be worth checking out.

Not normal.

The shop should drive it and fully re-inspect. It should be fairly obvious if the engine or trans mounts need replacement. If nothing turns up from the inspection, then its time to remove the transmission again

Might be worth checking the condition of the freewheel mechanism on your alternator.

Cruise RPM
 

So what is the best RPM to cruise at ??

My memory is going with old age. I was incorrectly recalling this Rennlist post I had seen a long time ago. Sorry about that!

6000...:)

I usually try to keep mine at about 32-3500ish. Never be afraid to rev a Porsche motor.