DMF replacement controversy

I recently had a difference of opinion regarding the automatic renewal of the DMF when the Clutch is replaced.
Following my comments regarding only replacing the DMF if it is faulty and the fact that a friend of mine who is a lR Independent specialist using a test rig to check the DMF which was scoffed at.
I have seen the rig and it is manufactured by Sykes Pickavant in collaboration with LUK Clutch division.
LUK advise that the DMF is checked for performance and condition with the rig against tolerances that they specify. If it meets the conditions, there is no need to change it. As I explained in my previous post, basically the rig checks for backlash (Play) in the unit and spring torsion. Obviously any visible mechanical problems or failures are taken into account.

Sorry for being thick, what the DMF please mate.

illy

Dual Mass Flywheel.....takes some of the snatch out when torque is applied

Dual Mass Flywheel. Until a few years ago the engine flywheel was a one piece solid wheel with a starter motor ring gear shrunk on to it.
A few years ago the idea came up to make the flywheel out of two separate parts. The first "Wheel" is driven directly from the crankshaft and there is another wheel which is free to move independently against basically spring pressure, from the first one, The clutch mechanism is attached to the second wheel.
One of the advantages of the DMF against the standard flywheel set up is that it is quieter and the torsional shocks involved with a standard flywheel are damped by the DMF springs.
Have a look on Google and they will explain things in greater detail than I have.

I had the pressure and clutch plate changed on my TD4 at around 70 thou. The DMF was checked visually and as there was no shudder problems it was decided not to replace. There has been no problems in the 15 thou miles it has done since then.

My personal thoughts are that there is a lot of paranoia created on this subject with many stating that the DMF must be changed when renewing the clutch due to possible wear and weakening of the springs etc. this has obvious advantages, financially for garages and suppliers.

The mechanical performance specifications for specific car models which have the DMF fitted are clearly laid out by the DMF manufacturer together with acceptable wear/weakness tolerances and they state that provided the DMF is within these limits and no physical damage has occured, it is not necessary to replace it.
Of course if the owner chooses to replace the unit regardless, that is entirely their choice.

generally its over 100 thou when clutch needs replacing ,and whilst your dmf might still be good ,most arent that i see ,after youve fitted a few without replacement then have to a short time after ,you start fitting as the norm, i think youd be very lucky for 1 dmf to see out 2 clutches

jamesmartin said:

generally its over 100 thou when clutch needs replacing ,and whilst your dmf might still be good ,most arent that i see ,after youve fitted a few without replacement then have to a short time after ,you start fitting as the norm, i think youd be very lucky for 1 dmf to see out 2 clutches

Click to expand...

:behindsofa:

Do you always check the condition and operation of the DMF to see if it is within specification ?- Providing there is no visible damage of course which will render it as scrap anyway.

i do ,then replace unless its very low mileage as normally they are worn ie end float or excessive travel

I know someone who put a ordinary flywheel on and then suffered a snapped crankshaft.

Plus don't some engines (like a five cylinder Td5) have 'harmonic imbalances' when running that the DMF is designed to cancel out?

My view is that if you have the gearbox off anyway then you might as well replace any part that will require the gearbox to be removed to be replaced when it [the part] wears out or fails.