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Dual Mass Flywheels
2

Dual Mass Flywheels

Dual Mass Flywheels

(OP)
When were DMF (dual mass flywheels) first installed on automotive vehicles ?

Does anyone have any statistics concerning the failure rate among different manufacturers / vehicles ?

Interesting as the concept is, I am not convinced that the advantages, e.g. reduced driveline noise/vibration,
outweigh the additional expense of the DMF itself and / or the reduced reliability factor inherent in the design as opposed to a single mass flywheel.

Can anyone tell me how long the DMF manufacturers warrant their flywheels to the OEMs ?

Should failure of a DMF be covered by the OEM, e.g. Volkswagen, under their stated powertrain warranty, if said failure causes a catastrophic failure of the clutch and renders the vehicle unusable?

Is it possible for the planet gears to strip out in a DMF and render a vehicle undrivable?

Is it possible for the grease in the DMF to leak out and contaminate the clutch disc, again rendering the vehicle undriveable ?

Do any OEMs authorize the replacement of a factory installed DMF system with a single mass flywheel system and still retain any unused powertrain warranty coverage ?

Comments ?

for more info:
http://www.luk.de/Bibliothek/Download/folien_zms.pdf

http://www.sachshandel.de/owx_medien/media141/14172.pdf


Thanks in advance,
Hunter

Bruce Toski
ASE Master Certification
Automotive Instructor

RE: Dual Mass Flywheels

First one I know of was ca 1985, but I am sure they were used long before then.

It is hard to believe that they will fail unless the vehicle is grossly abused. They will have been through the same durability sign-off as the rest of the vehicle and engine, as they are not a serviceable item.

I don't understand your comments about grease and planetary gears, perhaps you are not talking about a DMF at all?

Cheers

Greg Locock

RE: Dual Mass Flywheels

(OP)
Greg,
Please take a moment to view the links at the end of my post and then I hope you will understand where I am coming from.
Thanks,
BT

Bruce Toski
ASE Master Certification
Automotive Instructor

RE: Dual Mass Flywheels

Oh, OK. The second pdf wouldn't open when I tried earlier. I haven't seen an epicyclic type before, and have no experience with them.

I don't know the answers to any of your questions specifically, but would observe that suppliers don't really give us (OEMs) a warranty on their parts. If it fails during the warranty period they have a look at it and if the moon is blue they reimburse us for the repair costs. Basically we have to show that the part was not of the same standard as the prototype parts if we want to force the issue, which is very hard to do.

From reading the second pdf, if your DMF has shed grease they will claim it is user-abuse and it won't be covered under the warranty. The only exception to this would be if there was no sign of burning on the friction surface.

I doubt that they would offer different flywheels on the same engine/trans combination - the whole system would have to be revalidated.

Cheers

Greg Locock

RE: Dual Mass Flywheels

(OP)
Greg,
Thanks for the reply.
I am just searching for an answer.
Such quick failures of the clutch system (hydraulics are ok) seem to find their only explanation in a failure of this new DMF.  I have been fixing cars since 1973 and have never seen quick clutch failures except with tremendous abuse (not present herein).
Thanks.
BT

Bruce Toski
ASE Master Certification
Automotive Instructor

RE: Dual Mass Flywheels

Sorry, this the first time I've looked into dual mass flywheels, it appears to be simply a harmonic damper normally mounted on the accessory drive side integrated into the flywheel?  Is this correct?

Ken

RE: Dual Mass Flywheels

No, in a conventional DMFW the isolators are also the load path. You might be puzzled why this is any different to the springs in the centre of the clutch. What is actually happening is that the back half of the flywheel is directly coupled to the trans, and so increases the inertia on the driven side of the isolator. The springs in the centre of the clutch are heavily compromised by their size, the DMFW gives you more room to fit some damping into the system.

Cheers

Greg Locock

RE: Dual Mass Flywheels

so, the DMFW gives some of the effects of a much heavier flywheel?
Or the effect of a heavier flywheel plus torsional damping?

Jay Maechtlen

RE: Dual Mass Flywheels

Well, in practical terms it gives you better isolation at high frequency, so it is a bit like a heavy flywheel +torsional harmonic damper. However, there is a corresponding downside, the very low frequency performance can be worse as you added compliance into the driveline, so there can be surge problems. This is one reason that the more complex alternatives using hydrostatics were being investigated.

Cheers

Greg Locock

RE: Dual Mass Flywheels

(OP)
Here is the final outcome of my customer's 2001 Jetta with the failed clutch at 15,000 miles.

Dealer refused to honor this repair under the manufacturer's 10year 100,000 miles Powertrain Warranty.

Here are the arguments that I suggested to the customer to pursue equity in this matter:

1) We demanded to be there upon removal of the transmission and were not informed of when this was going to occur.  It was removed without either one of us present and therefore we have no guarantee that any of the components were originally installed on your car.    

2) The DMF (dual mass flywheel) is exhibiting play that exceeds that of a new unit. There is no spec. in the factory repair manual but a new unit I tested had 6mm play.  The one on your car has more than 22mm play !  Maybe even more important is that oil / grease appears to have leaked out from the DMF and contaminated the clutch disc and the whole inside of the bell housing.

3) The whole unit is under-engineered.  The new part number for the upgraded unit is 17-059 (LuK) and 06A 105 264M (VW).  This upgraded unit has a larger (230mm v 220mm OD) clutch disc. It should not wear out so quickly.

4) There are many reports similar to yours of early catastrophic clutch failures .. On the internet.

5) Key personnel at the dealer and at the company that manufactures the clutch units have confirmed several times the abnormal failure rate of this clutch unit, especially in 2000 and 2001 Jettas with 1.8 Turbo engines.

6) Just to the left of the input shaft to the transmission is an abnormal wear pattern on a static surface of the tranny that should not be there.  I believe that the bolts holding the pressure plate to the flywheel either broke or worked loose and allowed excessive movement of the pressure palte to contact the inside static surface of the transmission housing.  This is completely abnormal ..... Once again .... since they did not allow me to be there during teardown.... we can only assume they wish to hide something.  At this point I can not confirm my assertion since I do not even know where the bolts are now .......

7)VvW of NA has refused to advance this issue to the District Tech Rep so that is why we are issuing a final plea before sending out a Notice of Intent to Sue.

Bruce Toski
ASE Master Certification
Automotive Instructor

RE: Dual Mass Flywheels

Hey, somewhat off-topic, but in the Volkswagen factory service manual it specifically states to replace the flywheel if it is leaking fluid.

Some high-performance VW parts dealers are taking OEM flywheels and modifying them to remove the dual-mass gadgetry.  I don't know what this involves, but I've seen them.  (The original friction surface of the flywheel is retained.)

RE: Dual Mass Flywheels

(OP)
Thanks mikikanazawa,
I have checked my $65 Bentley manual and there is no mention of what you say in chapter 13 (engine) or chapter 30 (clutch).  Which manual and which page did you find this statement ?
This Bentley manual also does NOT have any spec for flyewheel play ..... how lame.

Bruce Toski

Bruce Toski
ASE Master Certification
Automotive Instructor

RE: Dual Mass Flywheels

Ford & GM used DMF's with the diesels. I have never seen one that was not junk. LUK has engineered kits that fix this mess. They use a solid flywheel and a conventional sprung hub disc. Problem solved. I think the idea was to damp out harmonics/shock loads from the diesel to the trans input shaft. Light duty drivelines + big diesel ft/lbs = Breakage. I have had DMF's resurfaced that had play, big mistake, clutch chatter like you would not believe. I am not familiar with these other DMF's just the truck ones that have the sprung hub. I think what is happening it the torque loads combined with the clutch heat 'un-tempers' the springs so the hub develops slop. I have seen about an 1" of rotational play in them. Perhaps the sealed fluid design  would hold up better with a seal material that can take 1000F temps.

RE: Dual Mass Flywheels

(OP)
Unfortunately the law firm that was considering implementing a class action lawsuit against VW for these lame DMF flywheels ... chickened out.  Individual owners will now have to sue VW in small claims court, one at a time.  I have talked with one owner who went ahead and installed the aftermarket solid flywheel kit and they are quite happy with it.  The whole thing is just a mess.  I would bet money that these failing DMFs are being manufactured in China to boot.  Only discovery in a lawsuit will find out for sure.
BT

RE: Dual Mass Flywheels

Interesting, Porsche had a similar problem with their 911 series from 1989 to late 1992.  ALL their Freudenberg flywheels would fail and they (the owner) replaced them with a model from LUK (absolutely no warranty repairs obviously).

RE: Dual Mass Flywheels

1. What did Porsche do after '92?
2. What was the longevity of the LUK units?
3. what's the difference between those old LUK units and the new ones?
4. I wonder what the actual failure rate of the current units is?

Jay

Jay Maechtlen
http://home.covad.net/~jmaechtlen/

RE: Dual Mass Flywheels

Possibly relevant. At one company I worked for, perfectly satisfactory (for normal drivers) OEM drivelines were rated for 50 standing starts 0-60 mph. So, if you treated your car like motoring journalists did, then it didn't last very long.

It didn't really matter, most were wrapped round trees long before the driveline gave out. Espeically when the journalists were driving.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Dual Mass Flywheels

Quote (JayMaechtlen):

What did Porsche do after '92?
  In 89-90 Porsche used the original Freudenberg and then in 91-92 they used a modified Freudenberg.  From 92 onward they switched to LUK.

Quote (JayMaechtlen):

What was the longevity of the LUK units

75-100,000+ miles, its the Freudenbergs that failed prematurely.

Quote (JayMaechtlen):

what's the difference between those old LUK units and the new ones?

The only difference I know of is the LUK thrust ring is riveted to the flywheel there is no separate lock ring or plate like the Freudenberg.

Quote (JayMaechtlen):


I wonder what the actual failure rate of the current units is?

Very rarely


RE: Dual Mass Flywheels

(OP)
Gents,
Thanks for the responses.
So Porsche is still using DMF flywheel setups in thier 911 cars?  If so, and if current units have a low failure rate I must ask ....
1) Why are the Jetta units failing and the Porsche aren't ?
2) What were the reason(s) for failures in the earlier Freudenberg units ?
3) Can one say unequivocally that the DMF "low failure" LUK units (in the Porsche) suffer a higher percentage of failure than the old type solid metal flywheel used with a standard pressure plate and clutch disk (with springs in the clutch disk)?

As you can see ... I still am not convinced of the "worthiness" of the DMF over the old standby.

Bruce Toski

Bruce Toski
ASE Master Certification
Automotive Instructor

RE: Dual Mass Flywheels

Quote (agent007):

So Porsche is still using DMF flywheel setups in thier 911 cars?  If so, and if current units have a low failure rate I must ask
Yes, Porsche is still using the DMF even in the high (450HP+) horsepower cars.

Quote (agent007):

What were the reason(s) for failures in the earlier Freudenberg units

The damper between the two masses fails and you end up with a clunking.  Porsche allowed upto 15mm of movement (with return) before they declared the flywheel dead.

Quote (agent007):

Can one say unequivocally that the DMF "low failure" LUK units (in the Porsche) suffer a higher percentage of failure than the old type solid metal flywheel used with a standard pressure plate and clutch disk (with springs in the clutch disk)?

I'm not sure I would call 100,000 miles out of DMF flywheel a failure.  I know there a some that have gone 150k+ miles.

Quote (agent007):

As you can see ... I still am not convinced of the "worthiness" of the DMF over the old standby.

When I replaced my clutch this past winter I swapped out the 32 pound LUK DMF for an 11 pound lightweight aluminum flywheel.  There is no way Porsche could use this on a normal street driven car, too many people would complain about the idle chatter and low RPM lugging sound.  The new CarreraGT basically doesn't have a flywheel (weighs 1 pound or something silly) and the owners are complaining about the noise.  The only other cars Porsche still uses a LWF is on their non-street legal race cars and homologation specials. (GT3RS, CupCar)

RE: Dual Mass Flywheels

(OP)
Interesting,
Thanks for the info and comments.
BT

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