Dual mass flywheels - signs of failure?
Discussion
Dual mass flywheels do make a differance, i fitted a solid flywheel & suitable clutch to a e46 330 clubsport & although the car drives perfectly at idle it sounds like the gearbox is about to fall out!! It is also quite juddery when pulling away although that may be more down to the uprated clutch than the lack of Dmf.
I wouldn't say that car makers fit dmf's for fun or to make money.
They are fitted to reduce engine vibration, not to protect the transmission from torsional vibration as a lot of people on here seem to think, that's the job of the clutch cush springs.
The part of the flywheel that the clutch mounts on will rotate at near enough a constant angular speed through each revolution at anything above idle whether a dmf or solid flywheel is fitted due to the mass and diameter of the flywheel (that and having somewhere to mount the clutch is what it's there for).
Although the flywheel rotates at a constant angular speed through each revolution, the front of the crankshaft does not, due to the twisting force on the crank caused by the compression and firing of each cylinder in turn (whith the greatest twisting force being caused by the cylinder at the opposite end to the flywheel)
Although a crankshaft front pulley damper is usually fitted to help damp it out, this twisting causes vibration.
The purpose of the DMF is to allow the rear of the crank and inner light part of the flywheel to rotate at a slightly varying angular speed through each revolution while the clutch face of flywheel does not thus reducing twisting and vibration.
Fitting a solid flywheel will cause a bit more vibration (from the engine, if it seems to be coming from somewhere else, it's being transmitted) but I still maintain they're piss poor idea as there effective life is quite short,
(the most common failuren symptom IS vibration).
If someone was to argue that fitting a solid flywheel will put extra stess on the crank, they may have a point, but I've not heard of problems with this. It's worth noting that most reputable clutch manufacturers make solid flywheel conversions, except LUK who hold the patent on dual mass flywheels.
They are fitted to reduce engine vibration, not to protect the transmission from torsional vibration as a lot of people on here seem to think, that's the job of the clutch cush springs.
The part of the flywheel that the clutch mounts on will rotate at near enough a constant angular speed through each revolution at anything above idle whether a dmf or solid flywheel is fitted due to the mass and diameter of the flywheel (that and having somewhere to mount the clutch is what it's there for).
Although the flywheel rotates at a constant angular speed through each revolution, the front of the crankshaft does not, due to the twisting force on the crank caused by the compression and firing of each cylinder in turn (whith the greatest twisting force being caused by the cylinder at the opposite end to the flywheel)
Although a crankshaft front pulley damper is usually fitted to help damp it out, this twisting causes vibration.
The purpose of the DMF is to allow the rear of the crank and inner light part of the flywheel to rotate at a slightly varying angular speed through each revolution while the clutch face of flywheel does not thus reducing twisting and vibration.
Fitting a solid flywheel will cause a bit more vibration (from the engine, if it seems to be coming from somewhere else, it's being transmitted) but I still maintain they're piss poor idea as there effective life is quite short,
(the most common failuren symptom IS vibration).
If someone was to argue that fitting a solid flywheel will put extra stess on the crank, they may have a point, but I've not heard of problems with this. It's worth noting that most reputable clutch manufacturers make solid flywheel conversions, except LUK who hold the patent on dual mass flywheels.
Edited by oakdale on Thursday 13th January 22:00
Old Merc said:
GSF & EURO do flywheel/clutch kits to replace DMF jobs.I agree,why do they fit these expensive DMF?? !! I`ve spent my time with Peugeot`s,in the old days never replaced a flywheel in my life and clutches could last 80-100K.Now clutches & DMF are replaced in under 50K at £1000 a time.!!
I boughy a conversion kit and the clutch springs broke. I bought a Luchs DMF and it has been perfect.
Pumaracing said:
stevieturbo said:
Although they are pretty much considered replacement items, despite their ridiculous price.
Why manufacturers insist on using these pieces of crap is beyond me
Seconded.Why manufacturers insist on using these pieces of crap is beyond me
lost in espace said:
Old Merc said:
GSF & EURO do flywheel/clutch kits to replace DMF jobs.I agree,why do they fit these expensive DMF?? !! I`ve spent my time with Peugeot`s,in the old days never replaced a flywheel in my life and clutches could last 80-100K.Now clutches & DMF are replaced in under 50K at £1000 a time.!!
I boughy a conversion kit and the clutch springs broke. I bought a Luchs DMF and it has been perfect.There is a gearbox specialist next to my unit,he changes these regularly and always tries to replace the dmf with a solid flywheel.
The guy that does manual gearboxes reckons a shagged dmf kills gearboxes quite rapidly because of the dead stop effect when it hits it`s stop,there isno torsional damping effect left as the cluch plates used with these dont usually have them.
Anyone with half a clue should be able just to feel and hear when one has had it and also the damage it will do to the box if left.
I had a scorpio with one once that had snapped a spring that wore through the pressed backplate and cut the back of the block to bits.
Never seen a solid flywheel do anything other than explode when its been milled too much or the gear ring falls off.
£500 for a flywheel and clutch every two years,yeah righto!
I think I will stick with the method that lasts.
After these dmfs have done 30k they all rattle and vibrate so wheres the benefit?
Same with harmonic balancers £300 for something that again lasts 2 years before it falls off.
Im all for progress as long as they get it right before foisting it upon us.
they have had fifteen/twenty years or so and clearly still cant get them right.
The guy that does manual gearboxes reckons a shagged dmf kills gearboxes quite rapidly because of the dead stop effect when it hits it`s stop,there isno torsional damping effect left as the cluch plates used with these dont usually have them.
Anyone with half a clue should be able just to feel and hear when one has had it and also the damage it will do to the box if left.
I had a scorpio with one once that had snapped a spring that wore through the pressed backplate and cut the back of the block to bits.
Never seen a solid flywheel do anything other than explode when its been milled too much or the gear ring falls off.
£500 for a flywheel and clutch every two years,yeah righto!
I think I will stick with the method that lasts.
After these dmfs have done 30k they all rattle and vibrate so wheres the benefit?
Same with harmonic balancers £300 for something that again lasts 2 years before it falls off.
Im all for progress as long as they get it right before foisting it upon us.
they have had fifteen/twenty years or so and clearly still cant get them right.
Max_Torque said:
seagrey said:
There is a gearbox specialist next to my unit,he changes these regularly
i'd bet a fiver that 1 in 3 DMF's that "require" replacement are actually fine.................even if you are being generous and said one in ten its still a massive difference to a solid flywheeel which probably fails at the rate of one in thousands.
I'm with Max Torque on this. Remember, there was a time when fuel injection was frowned upon as being too complicated and there was a brigade of folk who would have been happy to replace EFI with carbs, because that is what they understand.
Manufacturers wouldn't spend R&D money on a component, unless it brought an advantage to the products they are selling in what is probably the most competitive market anywhere. Also, I don't think manufacturers will stake their reputation on a component that is designed to fail.
I expect that most of the problems associated with DMF are due to wear and tear as a result of user's lack of mechanical sympathy. If someone is going through clutches every 10-15k mile, no-one suggests that the clutches are designed to fail to generate business for dealers and parts suppliers.
FWIW I have never had to replace a clutch on any car I have owned, and the DMF (and clutch) in my current run about are in fine fettle after 50k mile of my use, including trips to the 'ring. My guess is that if you are heavy handed (footed) you can expect issues.
Steve
Manufacturers wouldn't spend R&D money on a component, unless it brought an advantage to the products they are selling in what is probably the most competitive market anywhere. Also, I don't think manufacturers will stake their reputation on a component that is designed to fail.
I expect that most of the problems associated with DMF are due to wear and tear as a result of user's lack of mechanical sympathy. If someone is going through clutches every 10-15k mile, no-one suggests that the clutches are designed to fail to generate business for dealers and parts suppliers.
FWIW I have never had to replace a clutch on any car I have owned, and the DMF (and clutch) in my current run about are in fine fettle after 50k mile of my use, including trips to the 'ring. My guess is that if you are heavy handed (footed) you can expect issues.
Steve
stevesingo said:
I'm with Max Torque on this. Remember, there was a time when fuel injection was frowned upon as being too complicated and there was a brigade of folk who would have been happy to replace EFI with carbs, because that is what they understand.
Manufacturers wouldn't spend R&D money on a component, unless it brought an advantage to the products they are selling in what is probably the most competitive market anywhere. Also, I don't think manufacturers will stake their reputation on a component that is designed to fail.
I expect that most of the problems associated with DMF are due to wear and tear as a result of user's lack of mechanical sympathy. If someone is going through clutches every 10-15k mile, no-one suggests that the clutches are designed to fail to generate business for dealers and parts suppliers.
FWIW I have never had to replace a clutch on any car I have owned, and the DMF (and clutch) in my current run about are in fine fettle after 50k mile of my use, including trips to the 'ring. My guess is that if you are heavy handed (footed) you can expect issues.
Steve
The fact that DMF replacement is almost in pandemic proportions....mean there arent just a few isolated cases. It clearly is a major problem.Manufacturers wouldn't spend R&D money on a component, unless it brought an advantage to the products they are selling in what is probably the most competitive market anywhere. Also, I don't think manufacturers will stake their reputation on a component that is designed to fail.
I expect that most of the problems associated with DMF are due to wear and tear as a result of user's lack of mechanical sympathy. If someone is going through clutches every 10-15k mile, no-one suggests that the clutches are designed to fail to generate business for dealers and parts suppliers.
FWIW I have never had to replace a clutch on any car I have owned, and the DMF (and clutch) in my current run about are in fine fettle after 50k mile of my use, including trips to the 'ring. My guess is that if you are heavy handed (footed) you can expect issues.
Steve
And the fact people are replacing them with solid flywheels with no negative effects to their cars...again, seems DMF's arent all they are cracked up to be.
And DMF's are classed as items to be replaced every clutch or 2nd clutch. It seems plenty dont even last that long. That is a serious problem.
stevesingo said:
I'm with Max Torque on this.
I expect that most of the problems associated with DMF are due to wear and tear as a result of user's lack of mechanical sympathy. My guess is that if you are heavy handed (footed) you can expect issues.
Steve
thats the whole point, a solid flywheel will get wear and tear so will a dmf but they bring a whole new range of problems that werent there before.I expect that most of the problems associated with DMF are due to wear and tear as a result of user's lack of mechanical sympathy. My guess is that if you are heavy handed (footed) you can expect issues.
Steve
I know some seriously heavy footed drivers but never heard of one breaking a standard solid flywheel.
anyway its supposed to take some stick.
what is the advantage to having something costly that was developed to contain vibration,noise and to smooth the drive of the vehicle or save the gearbox depending on your take, when it fails prematurely creating more noise,vibration and harshness than it masked in the first place and then causing wear or damage to your box as well.
then costing more to replace than any long term saving over the life expectancy of the gerabox,there are plenty of powerful cars reliably using standard factory gearboxes with out dmf`s.
these things are desgined and balanced to work when they are new there is no tolerance for slight wear,even a little bit of throw out or backlash is defeating the object.
Manufacturers are not bothered by the fact that when you buy it 3 years down the line from some car supermarket or off someones door step it sounds and feels like a misfiring cement mixer.they just want it to be 0.0006dcb quieter than the rival
when its new.
Had another DMF job today, Peugeot 407SW Est 2006 with 53k on the clock!!£900 for parts!!!! that is terrible.I`ve spent most of my time with Peugeot`s and the old 405,505 406 etc clutches would last 100K and a flywheel was just a lump of metal that stayed on the engine for ever.We also used Peugeot estates and vans as rally tow trucks with normal clutches with out a problem.I still say about DMF, why fit them?
stevieturbo said:
And the fact people are replacing them with solid flywheels with no negative effects to their cars...again, seems DMF's arent all they are cracked up to be.
The thing is... people only change to a solid flywheel when the DMF has problems. If they change a DMF which has deteriorated unnoticed over time, and don't notice a difference, it may not be that a new solid flywheel is better than a brand new DMF.I'm not saying DMFs don't have their problems, but we should compare apples with apples.
I`ve always been anti DMF and suggested here fitting solid flywheel/clutch kits , BUT...Since talking to a very knowledgeable motor engineer this may be not a good idea?? apparently there have been a number of cases,(Skoda snapping a crankshaft and a VW cracking a gearbox)blamed on converting from DMF to solid!! saying these engines are designed around a DMF. Any comments on this guys??
Old Merc said:
I`ve always been anti DMF and suggested here fitting solid flywheel/clutch kits , BUT...Since talking to a very knowledgeable motor engineer this may be not a good idea?? apparently there have been a number of cases,(Skoda snapping a crankshaft and a VW cracking a gearbox)blamed on converting from DMF to solid!! saying these engines are designed around a DMF. Any comments on this guys??
Had a golf tdi that knocked out 2 sets of big ends the second time a short block was fitted with a dmf but had no more problems was never sure if it was the solid flywheel but its the only tdi ive ever seen with big end problems 
bobthepsycho said:
stevieturbo said:
And the fact people are replacing them with solid flywheels with no negative effects to their cars...again, seems DMF's arent all they are cracked up to be.
The thing is... people only change to a solid flywheel when the DMF has problems. If they change a DMF which has deteriorated unnoticed over time, and don't notice a difference, it may not be that a new solid flywheel is better than a brand new DMF.I'm not saying DMFs don't have their problems, but we should compare apples with apples.
That's only my one off experience though.
buggalugs said:
bobthepsycho said:
stevieturbo said:
And the fact people are replacing them with solid flywheels with no negative effects to their cars...again, seems DMF's arent all they are cracked up to be.
The thing is... people only change to a solid flywheel when the DMF has problems. If they change a DMF which has deteriorated unnoticed over time, and don't notice a difference, it may not be that a new solid flywheel is better than a brand new DMF.I'm not saying DMFs don't have their problems, but we should compare apples with apples.
That's only my one off experience though.
This seems to sound OK
http://www.youtube.com/watch?v=_9t6vSLYUcQ
But I really wouldn't want this....
http://www.youtube.com/watch?v=hqhHF14EjvU
Mark34bn said:
buggalugs said:
bobthepsycho said:
stevieturbo said:
And the fact people are replacing them with solid flywheels with no negative effects to their cars...again, seems DMF's arent all they are cracked up to be.
The thing is... people only change to a solid flywheel when the DMF has problems. If they change a DMF which has deteriorated unnoticed over time, and don't notice a difference, it may not be that a new solid flywheel is better than a brand new DMF.I'm not saying DMFs don't have their problems, but we should compare apples with apples.
That's only my one off experience though.
This seems to sound OK
http://www.youtube.com/watch?v=_9t6vSLYUcQ
But I really wouldn't want this....
http://www.youtube.com/watch?v=hqhHF14EjvU
I used an M20b20 flywheel and M20b25 sprung clutch, which I guess is in the ballpark of what the guy in the first vid has got.
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