-
TDR Magazine subscribers receive more than the magazine! You also gain additional forum privileges!
Details here: TDR Privileges
Subscribe to TDR Magazine here: https://www.tdr-online.com/
Anyone have pictures of Dual Mass flywheel?
- Thread starter Motorhead
- Start Date
Attention: TDR Forum Junkies To the point: Click this link and check out the Front Page News story(ies) where we are tracking the introduction of the 2025 Ram HD trucks.
Thanks, TDR Staff
- Status
What is the DMF's function? It is designed to isolate torsional crankshaft spikes created by diesel engines with high compression ratios. By separating the mass of the flywheel between the diesel engines and the transmission, torsional spikes can be isolated, eliminating potential damage to the transmission gear teeth.
The dual mass systems are designed to transmit less engine vibration to the driveline, and give a better more car like driving experience. They also reduce some of the jarring and stress on the transmission and remainder of the drivetrain. They work fine as long as the engine remains unmodified and the vehicle is not used/abused beyond manufacturers recommendations.
As soon as you start to increase the engine power over stock, or load the vehicle beyond design parameters, you run into problems. Dual mass flywheels are tuned systems and must be matched to the engine torque curve, engine resonant characteristics, vehicle load curves (including axle ratio/tire size calculations). They work by having a set of springs inserted between two rotating masses (thus dual mass). The springs are sized to soak up some of the resonant vibration from the diesel engine under load conditions. A dual mass fly wheel generally also contains an over torque friction release, so if it gets suddenly overloaded, rather than damage the springs, it slips. This works fine as a safety valve, but if it does it much it burns up. In short, overloaded they burn up and the springs get destroyed and they are worse than if it were a single mass FW.
The single mass part WILL tend to transmit more engine pulse (vibration) tot he drivetrain, and will seem a bit rougher. But it is straight forward to design a single mass flywheel and clutch package for pretty much any engine torque curve and vehicle loading combo you can come up with. Drives more like a TRUCK, but has much better reliability at extreme use levels.
I think Dodge went with DMF's with the G56 manual trannies and I believe it's a single disk. I could not find a good picture, sorry. From what I read about them if you replace the clutch it's a good idea to do the flywheel as well or it's recommended being that they do wear out. The prices are through the roof on them as well, upwards of $500 or more.
The dual mass systems are designed to transmit less engine vibration to the driveline, and give a better more car like driving experience. They also reduce some of the jarring and stress on the transmission and remainder of the drivetrain. They work fine as long as the engine remains unmodified and the vehicle is not used/abused beyond manufacturers recommendations.
As soon as you start to increase the engine power over stock, or load the vehicle beyond design parameters, you run into problems. Dual mass flywheels are tuned systems and must be matched to the engine torque curve, engine resonant characteristics, vehicle load curves (including axle ratio/tire size calculations). They work by having a set of springs inserted between two rotating masses (thus dual mass). The springs are sized to soak up some of the resonant vibration from the diesel engine under load conditions. A dual mass fly wheel generally also contains an over torque friction release, so if it gets suddenly overloaded, rather than damage the springs, it slips. This works fine as a safety valve, but if it does it much it burns up. In short, overloaded they burn up and the springs get destroyed and they are worse than if it were a single mass FW.
The single mass part WILL tend to transmit more engine pulse (vibration) tot he drivetrain, and will seem a bit rougher. But it is straight forward to design a single mass flywheel and clutch package for pretty much any engine torque curve and vehicle loading combo you can come up with. Drives more like a TRUCK, but has much better reliability at extreme use levels.
I think Dodge went with DMF's with the G56 manual trannies and I believe it's a single disk. I could not find a good picture, sorry. From what I read about them if you replace the clutch it's a good idea to do the flywheel as well or it's recommended being that they do wear out. The prices are through the roof on them as well, upwards of $500 or more.
Last edited:
I KNOW a lot of people with modified trucks and DMF, myself included and have had NO PROBLEMS! THE SKY IS NOT FALLING. So far they seem to hold up well. I have one sitting in my garage, as far as I can tell the clutch cover has a wedge shape that adds plate pressure if it starts to slip. This explains why that the peddle required more effort to push after a hard run. I think that they will/have proved themselves to be reliable.
DMF Pictures
https://www.turbodieselregister.com...missions-2003-2007/177952-dmf-issue-06-a.html
This link has a picture of the center section of the G56 DMF and some comments about DMF's. The G56 uses a single plate disc.
Bob V, the wedge that you are seeing is not to add clampload, it is part of the self adjusting clutch system. It compensates for the disc gettting thinner.
https://www.turbodieselregister.com...missions-2003-2007/177952-dmf-issue-06-a.html
This link has a picture of the center section of the G56 DMF and some comments about DMF's. The G56 uses a single plate disc.
Bob V, the wedge that you are seeing is not to add clampload, it is part of the self adjusting clutch system. It compensates for the disc gettting thinner.
Check here:
LuK | Products | Dual Mass Flywheel (DMF)
and be sure to click on details at the bottom of that page too.
LuK | Products | Dual Mass Flywheel (DMF)
and be sure to click on details at the bottom of that page too.
Last edited by a moderator:
What I might add is our experience with Ford DMF's. Over the past 10 years we have replaced at least 250 Ford DMF's with a kit that uses a solid flywheel... .
In my best estimate, at least 60% of the failures are from a flywheel that fails before the clutch... . The Ford system uses plastic to hold the springs in place and once the plastic heats and cools it will break and either cause a vibration or later the flywheel will slip... . The customer thinks the clutch is slipping... .
I'm sure that Gary with Perfection has seen hundreds more of these than I have but the stories are hard to deal with... . most customers won't listen when you tell them the flywheel is at fault and often wish to purchase another clutch and grind the flywheel... .
The solid flywheel we've been selling with a clutch kit that has a new design disc does a fair job in dealing with the vibration as mentioned above but some of it still carries through to the transmission...
We have owned several Fords that are worked and we changed out each of the DMF's upon failure with the solid version... . in at least 800K miles on 4 trucks we never had to go back and do transmission work on them... when we'd wear out the clutch we'd grind the flywheel and install a new clutch...
All of our trucks have a 4 paddle Kevlar disc using an 8 spring center like a 14" Spicer disc. This disc is rated at 600 ft lbs of torque and seems to function well except for some light chatter backing up and in low with very heavy loads above 15K lbs of trailer weight... .
On the Fords our failures have been the center of the disc will eventually fail due to the shock loading of the 12 7/8 or 13" disc pulling trailers in the 15 to 20K lb range... ... again remember our trucks are loaded 85% of the time... ... Our 04 Dodge Dually pulled a 20K lb trailer for 240K miles before we turned it into an intown truck... ... we can't remember going through a tank of fuel with this truck empty!!
We have learned to bore out the small pilot bearing on the flywheel and install a large ball bearing, that's sealed and uses a full synthetic grease. This has saved the input shaft when the tiny needle roller bearing fails and turns to dust... .
In my best estimate, at least 60% of the failures are from a flywheel that fails before the clutch... . The Ford system uses plastic to hold the springs in place and once the plastic heats and cools it will break and either cause a vibration or later the flywheel will slip... . The customer thinks the clutch is slipping... .
I'm sure that Gary with Perfection has seen hundreds more of these than I have but the stories are hard to deal with... . most customers won't listen when you tell them the flywheel is at fault and often wish to purchase another clutch and grind the flywheel... .
The solid flywheel we've been selling with a clutch kit that has a new design disc does a fair job in dealing with the vibration as mentioned above but some of it still carries through to the transmission...
We have owned several Fords that are worked and we changed out each of the DMF's upon failure with the solid version... . in at least 800K miles on 4 trucks we never had to go back and do transmission work on them... when we'd wear out the clutch we'd grind the flywheel and install a new clutch...
All of our trucks have a 4 paddle Kevlar disc using an 8 spring center like a 14" Spicer disc. This disc is rated at 600 ft lbs of torque and seems to function well except for some light chatter backing up and in low with very heavy loads above 15K lbs of trailer weight... .
On the Fords our failures have been the center of the disc will eventually fail due to the shock loading of the 12 7/8 or 13" disc pulling trailers in the 15 to 20K lb range... ... again remember our trucks are loaded 85% of the time... ... Our 04 Dodge Dually pulled a 20K lb trailer for 240K miles before we turned it into an intown truck... ... we can't remember going through a tank of fuel with this truck empty!!
We have learned to bore out the small pilot bearing on the flywheel and install a large ball bearing, that's sealed and uses a full synthetic grease. This has saved the input shaft when the tiny needle roller bearing fails and turns to dust... .
Sounds like this would be increasing the plate load then. I guess I will have to do some more looking at the clutch cover I have. Anyway, I still say the Dodge DMf has NOT been a big problem as of yet, and I think that there is no reason to worry about it.
Failure Rate = ?
Bob V,
We do not have a failure rate on these DMF's but I have one in our lab that a TDR member sent to us showing the out of balance failure mode. I have seen this several times on TDR posts.
Fortunately the G56 DMF is not as complicated as the 7. 3L version, those have about 120 pieces (by my count, down to the rivets). The G56 version DOES NOT have the torque limiting feature like the 7. 3L does.
Bob V,
We do not have a failure rate on these DMF's but I have one in our lab that a TDR member sent to us showing the out of balance failure mode. I have seen this several times on TDR posts.
Fortunately the G56 DMF is not as complicated as the 7. 3L version, those have about 120 pieces (by my count, down to the rivets). The G56 version DOES NOT have the torque limiting feature like the 7. 3L does.
G56 DMF Pictures
As requested earlier, this is an actual used G56 DMF, and I included one image of a 7. 3L disassembled for grins. The numbers on the back of the second image are the gram centimeters imbalance that we measured on our Hines balancer due to the bushing wear that allowed the secondary to orbit. When it orbits, it is also carrying the cover assembly with it and the imbalance is a LOT more.
As requested earlier, this is an actual used G56 DMF, and I included one image of a 7. 3L disassembled for grins. The numbers on the back of the second image are the gram centimeters imbalance that we measured on our Hines balancer due to the bushing wear that allowed the secondary to orbit. When it orbits, it is also carrying the cover assembly with it and the imbalance is a LOT more.
I have a 16 with 12k miles dual mass springs broke and had a harsh noise on shut down*
- Status
Issue 128 – Digital Version
Digital Magazines
FREE!
TDR Test Drive - Digital Edition
Renew
Subscribe
Gift Subscriptions
Back Issues
Subscription Status
Address Change Form
Buyer's Guides
Ram Diagnostic Trouble Codes
The Perfect Collection
The Perfect Collection Vol. II
TSB Updates
Dodge/Cummins Historical Overview
Cameron Collection
What Makes Us Tick?
Product Showcase
Advertising
Turbo Diesel Register
Issue 128 – Digital Version
Digital Magazines
FREE!
TDR Test Drive - Digital Edition
Renew
Subscribe
Gift Subscriptions
Back Issues
Subscription Status
Address Change Form
Buyer's Guides
Ram Diagnostic Trouble Codes
The Perfect Collection
The Perfect Collection Vol. II
TSB Updates
Dodge/Cummins Historical Overview
Cameron Collection
What Makes Us Tick?
Product Showcase
Advertising
