OK, what is up with these dual mass flywheels? Are they there to protect our drive-trains from the nasty vibrations and torque spikes of the big bad Cummins or are they there for creature comfort, so you can drive your CTD to the opera in luxury?

Mine was slipping on #2 with the Jr so I figured that after 60K miles and maybe a rough former life the clutch had seen better days. (I really need to get a digital cam so I can post pictures of this thing.) It is not shot; it is just a waste of metal.

My pressure plate and the flywheel still have the original machining groves; there is no warping, cracking or discoloration, just a bit of clutch dust. The clutch dist itself still has lots of friction material left, at least 1/8” on each side. Now some of the friction material has some really, really small cracks, but nothing out of the norm.

The flywheel friction surface itself looks like it is tapered, (it is) it is about 2.5 inches, wide, or across, but the friction disk is only using the outer 1.5.” The inner inch or so with the rivet holes looks like the friction disk has never touched it.

The flywheel with the friction surface (flywheel #2) is only as thick as the pressure plate; this compounded with the 1.5” that is in contact will produce a lot of heat with no where to go if it slips at all. A big ole, flat thick flywheel can absorb much more heat before it gets hot. Any chatter with a DMF and you lose all torque transmission.

You can spin flywheel #2 so the outer diameter moves about ˝” before it contacts the primary flywheel via a bunch of springs. They might as well make a clutch out of rubber bands and paper mache. This thing has more springs than Spring Mountain!

WTH, haven’t diesel engines with manual transmissions and regular flywheels been around for like 100 years with no problems? I little searching shows that other manufactures have issues with dull mass flywheels in their diesel vehicle they make for Europe.


Tell me I'm not the only one!!!!

 

It's there for the same reason that we have silencer rings and intake silencers. To keep it from sounding and behaving like a diesel.

 

I already gutted that intake silencer, the DMF is a boat anchor in favor of a SBC, and I think I’ll tear out that turbo silencer just for spite!

 

So, a SBC DD will take care of this problem? B/c i want a newer truck but i'm scared I won't like the G56.

 

Yes. I have the 3600 DD Spring Hub and I love it. It replaces the flywheel. It's a little grabby when backing up a trailer but it's not too bad. Good street manners, launches with no problem. I have a G56 and love it. I've drove several with an NV5600 and I prefer the G56. It shifts much easier. Anytime you go with a dual disc it will make it a little harder to shift. I'm not big on the shifters in the 06 and up trucks tho. They have a different bend to them compared to mine.

If you know someone with a G56 see if they'll let you drive it, or find one on a lot somewhere. If you can, drive an 05 with a G56 then an 06 or 07. You'll see the difference I'm talkin about.

 

Thanks solar yellow. Love the color man.

 

Thanks. It's a love/hate color. Everybody I talk to either loves it or hates it. I just like bein different.

 

DMF's make drivability better. The extra mass keeps the motor spinning better, which results in the clutch engagement being much softer. They've been in 'luxury' sports cars for quite some time. It also keeps the motor spinning longer between shifts - again to make the ride smoother and not jerky. I've not been inside a dodge version, but my 'Vettes had them. The thing I hated about them was the difficulty in machining. This is because of the spring mechanism on the friction surface and the flywheel plate. So you can't properly replace a clutch without buying a flywheel as well. The single mass flywheel will allow the engine to rev faster. There is give and take with these things. They stink for hot rodding / racing, and they cost a lot to replace. The single mass wheels make things more herky jerky, but are great for road racing.

 

You're kidding right? It's to reduce harmonics produced by the engine.(ie combustion pulses) The outcome of the harsh harmonics with out it are gear train rattle at low rpm. If you have a pre 05 truck, go out and lug the motor, off thottle in a parking lot. That's rattle is your driveline. That's what it's all about. The new power level in 05 made that condition worse and deemed non comercial.

 

No, but you do bring up the other reason for them. Overall, they make the drive smoother and that's the bottom line right?

 

Nothing in my opinion has caused as much controversy in todays drivetrains as DMF's. We have had Solid Flywheels for many years and now our trucks are seeing DMF's. Ford was the big one one using them from the first 7.3L up to 1997, then they discontinued them in favor of the 13" solid that they used from '99 to the end of the 7.3L.

This is a quote from the SAE Manual Transmission Clutch Systems, Publication AE-17, page 88.

"Dual-Mass Flywheel Major Advantages
1) The DMF prevents gear rattle at idle and throughout the entire speed range in both drive and coast modes. Note that some DMF's require an idle stage damper in the flywheel or clutch damper because idle resonance is not solely a resonance phenomenon." Text continues.

I think to put it into simpler terms, the function of a DMF is to act as a filter in the driveline ahead of the trans to minimize the pulses in the flywheel BEFORE they get to the transmission and make noise in the gearbox.

We have all seen the push for more civilized, creature comfort orientated cabs, increased MPG, reduced vehicle weight and increased performance. The DMF plays a role in the 3rd Gen I think in part because the G56 benifits from it, and we have seen an increase in the "technology" in clutch discs (torsion damper) as the weight has been shaved, light weight alloys have replaced cast iron and a host of contributing reasons.

My .02$

I have a '05 NV5600, '97 NV 4500 and drive a company owned '07 G56 every so often.