what is the purpouse of a dual mass fly wheel

[tank140]

Hi all

sounds like a silly question but what is the exact purpouse of a dual mass fly wheel?

any info greatfully exepted

cheers
tank

[JohnC]

To dampen internal engine vibrations.

[Robyn]

Sadly the suckers are more trouble than they are worth.

Install a viscous damper up front and be done with the issue


Missy

[More Power]

Hi all

sounds like a silly question but what is the exact purpouse of a dual mass fly wheel?

any info greatfully exepted

cheers
tank

Tank,

A diesel engine generates significant momentary torque spikes in the crankshaft as each cylinder fires. A harmonic damper used on the front of the crankshaft helps to protect the crankshaft, while a dual-mass flywheel helped to protect the transmission and drivetrain. If these torque spikes are not reduced in some way, a failure of some component in the drivetrain becomes more likely. The dual-mass flywheel absorbs the worst of these torque spikes aft of the engine.

In practice, the original dual-mass flywheels as used by GM in the 6.2/6.5 and the Duramax, all or mostly all fail after some amount of use. Absorbing torque spikes over time takes its toll. GM eventually switched to a single-mass flywheel for the 6.5, but added springs to the clutch plate - to absorb the spikes. These seem to hold up fine.

Jim

[JohnC]

GM eventually switched to a single-mass flywheel for the 6.5, but added springs to the clutch plate - to absorb the spikes. These seem to hold up fine.

Wasn't there also a dampener added to the trans output shaft?

[More Power]

Wasn't there also a dampener added to the trans output shaft?

Yes, the complete single-mass FW retro-fit kit offered through GM did include a damper for the NV4500, but I'm not sure where it was located. As things usually go, most of those trucks that were later upgraded with the single-mass FW didn't get the trans damper installed. Haven't heard much about trans problems as a result, so I don't know how important the damper was to overall transmission longevity.

As a point of interest, all of the Duramax equipped trucks come with a damper fixed to the rear differential input yoke. I suspect this helps to prevent driveline "ringing", which I have some experience with back in the 90's in a 6.2L diesel / TH700R4 powered pickup. Ringing can sometimes be produced by the individual cylinder's torque spikes resonating in the hollow rear driveshaft.

Jim

[tank140]

Hi all

Thanks for the reply,

with ref to the dual mass FW is i right that the center portion of the FW (the bit where the clutch bolts to) moves by 1/8 of a turn when tryed by hand, i have one here on the bench, i was thinking of using it for a conversion but not sure because of the free moving bit?
what about using this FW and welding the moving bit so making a solid FW?

cheers
tank

[NH2112]

Hi all

Thanks for the reply,

with ref to the dual mass FW is i right that the center portion of the FW (the bit where the clutch bolts to) moves by 1/8 of a turn when tryed by hand, i have one here on the bench, i was thinking of using it for a conversion but not sure because of the free moving bit?
what about using this FW and welding the moving bit so making a solid FW?

cheers
tank

My F350's DMF is starting to make more noise from time to time, so at some time in the near future I'm going to swap in a solid flywheel kit ($500 dealer cost on our NAPA account.) However, if the GM DMF is designed the same way as the Ford's, maybe the Lucky Mod (http://good-times.webshots.com/album/568764837KzVToS) for converting a DMF to a solid can be used. Basically you take out the dampener springs and the friction material between the sections, bolt the 2 sections together, and use a clutch disc with springs in the hub.

You can find clutches & flywheels, both DMF & solid, here (http://www.clutchcityonline.com/gmc_pickup_65.htm).

[JohnC]

is i right that the center portion of the FW (the bit where the clutch bolts to) moves by 1/8 of a turn when tryed by hand,

Correct. Pretty much no friction.