Dispel the Myth of the Dual Mass Clutch Problem!

[Porschedude]

Dispel the Myth of the Dual Mass Clutch Problem! The problems reported with the early 964 Clutch is not really a problem with the Dual Mass Flywheel. Many car manufactures have gone to the Dual Mass Flywheel to reduce the vibrations within the engine. Chevy, Ford, and a few more have been using the Dual Mass Flywheel for a few years; years after Porsche started. The Dual Mass Flywheel is a great piece of engineering work. It can be fine tuned during R&D Engineering to dampen out all kinds of vibration. The modern V-8 internal combustion engine has used vibration dampers on the front of the engine, but are rather simplistic by comparison to a D-Mass.
Luk is one of the major manufactures and has a pretty fair article with cross-sectional views showing how they work. The figures require a little study to figure them out, due to the complexity.

http://www.luk.de/Bibliothek/Download/folien_zms.pdf

Where I see a myth is that many refer to the problem as a Dual Mass problem, but it is actually a Friction Disk problem. I suspect that the problem rubber center disk was introduced at the same time in the 964 as the Dual Mass. I think of the clutch as many parts, not one. The clutch cover or pressure plate has the same general configuration as it has for years. Only the Flywheel and the disk were new to Porsche. I am about to replace the friction disk in my C2 with 104,000 miles and I am unsure of what disk is installed. The engine was removed and de-flanged by the dealer during the first and previous owner in 1995. The Porsche Factory Warranty shows the de-flanging and the re-flanging only. It doesn’t show a disk change out.

Dual Mass Flywheels do have problems, they are a mechanical device and does wear out at some point. They do have a higher wear out rate than a standard single mass flywheel. An acquaintance of mine, who works on 911’s, 964’s, 993’s, 996’s and Boxsters exclusively in the SF Bay area, drove and listened to my ’91 C2 and said he heard the tell tail rattle when he shut it down. This was at 90,000 miles and two years ago and it hasn’t increased in amplitude at all. I am changing out all of the components because I feel it is time. I do hear the rattle when I shut down the engine.

[Britwrench]

I don't think there is any myth over the failure of the early DMF.
There were some, but it was over sensationalised as usual, failures where the DMF either locked up and caused vibrations or leaked the fluid out and rattled.
The rubber hub clutch was only installed in the first year of 964 production so the do not have a DMF and rubber hub clutch installed together. I have seen the early (non-Luk) DMF last for 115,000 so they weren't all bad.

I have no idea what de-flanging is, maybe you would like to elighten me?

[Porschedude]

De-flanging and re-flanging were the terms used by the factory in the service history report. In other words, "Disconnected the engine from the transmission and then reconnected. I was given a copy of a report on my car of which service procedures were performed and when.

I was unaware that the DMF had any fluid in it, I thought the rubber hubed clutch disk had the fluid. I remember something about the 944 had this problem of leakage, or was it the motor mounts...

chears,

[BudTaylorUS]

My 1990 DMF Failure lasted 18 year before dying. As I plan on keeping the car the RS set up is going back in...its a p-car not a lexus or something arent we supposed to enjoy the "good vibrations"....

[Pingo]

The new Porsches (incl. 997 GT3) uses dmf.

[john walker's workshop]

you replace them as a "complete" clutch job anyway, so it's not really an issue, it's just an expensive clutch job.

[Candelaria]

Once you go to a LWF, you don't want to go back, the difference is night and day, a proper sports car should not have a dual mass period.

[bigchillcar]

i have a lwf in my '90 964 C4 with a cyntex chip. stalling or poor idle problems are often mentioned to be associated with the swap to a lwf, especially with a/c. the idle in mine's not perfect, but hardly noticeable as an 'issue'. steve wong's chip would make mine even better, as he can map it to compensate for this. i agree - stay wit the lwf..it's a helluva nice feeling.