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TD5 Dual Mass Flywheel


Mark
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I am in the process of changing the clutch on my TD5 defender...

I am in 2 minds about whether to change the flywheel whilst I am at it - On the one hand, it makes sense to do it whilst it is apart, as I am aware they can be troublesome, however, on the other hand, I have no reason to suspect this one, and they are stupid expensive to replace. Does anyone have any accumulated wisdom to add to my dilemma?

My other issue is if I were to change it, do I go for another dual mass item or a much simplified single mass flywheel from the likes of rakeway?

Any contributions much appreciated.

Cheers

Mark

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As I understand it the dual mass flywheel dampens out sound, especially at tick over and reduces vibrations/juddering at low revs.

So if you are not bothered by increased noise and juddering at low revs then you can change it out for a single mass one.

Also as a DMF allows you to be in a higher gear at a given speed, it's likely that you'll see a slight drop in mpg if you abandon it. This seems to be backed up by more and more manufacturers adopting dual mass flywheels to improve mpg/CO2.

Cheers

Steve

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Also as a DMF allows you to be in a higher gear at a given speed, it's likely that you'll see a slight drop in mpg if you abandon it. This seems to be backed up by more and more manufacturers adopting dual mass flywheels to improve mpg/CO2.

How does that work? Surely dampening out vibration can't make that much of a difference? :unsure:

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the dual mass is there to damp out vibrations, the good old noise, vibration,harshness that manufacturers talk about - passenger comfort stuff - and also to allow the engine to spin up faster at low revs. The first stage of the flywheel makes it light, then when a certain engine speed is reached it gets heavier via centrifugal force. i have heard from various sources that changing to a solid version could possibly lead to engine damage, as the vibrations then travel down the crank and mainshaft in the box.

transits are the main ones to watch, as i have heard of instances of big end damage from replacing the DMF.

there should be a way of checking the spring force in the DMF, the only other way to check is to look for cracks and blueing of the surface, if in any doubt - change it, it's easier to do the job once than have to do it again in 6 months time.

what is the mileage? if it's over 70k, then i would swap it anyway.

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The milage on the truck is 150k so if it hasn't been done, it is probably due one. Just been quoted over £400 for the part from LR main dealer though, which puts me off the idea a bit though...

Cheers

Mark

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A dual mass flywheel is just two thinner steel flywheels joined by a bonded rubber compound and a set of springs that act as a damper. The dual mass flywheel is as heavy as if a normal steel flywheel had been fitted, so how would it allow the engine to spin up quicker? There is no centrifugal magic.

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I changed mine a while ago (in a Discovery) and was advised that if there was more than about 10mm of rotational "play" either side of centre then it was worth changing the flywheel - but I paid a lot less for one than you have been quoted. Try a local motor factor or an independent specialist for a price.

Peter

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The milage on the truck is 150k so if it hasn't been done, it is probably due one. Just been quoted over £400 for the part from LR main dealer though, which puts me off the idea a bit though...

Cheers

Mark

Wow, I had to replace the DMF on the wifes Shogun just before christmas, a 3.2 DID at 80k. It gets used off road and tows a lot. £1300 for the flywheel, clutch and bearing. Thats non gen kit too which just happened to be exactly the same manufacturer as the original i took out, even down to the mitsubishi stamp. As for transits we have a pool transit on the rental fleet out on contract hire, its done 170k and has had a replacement solid flywheel since about 20k with no ill effects or noticeable vibration or noise. As for my landrover, purchasing it seems to get further and further away... We have signed up for a mortgage and a house...

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I don't know if it would have the same effect on a Land Rover but when the clutch was due on my 2001 Skoda Octavia TDi recently I changed the DMF to a conventional one. The DMF needs to be changed on each clutch change where as the conventional flywheel doesn't (unless it is damaged).

What I found was that there is absolutlely no vibration or noise issue.

No difference in the use of gears.

No difference in the low rpm lugging (I can still pull away on tick over in 3rd or 4th and pull a trailer at 30mph in 5th).

Fuel consumption had been worse for a while prior to the change and has since been as good as new. The DMF springs were slack and it incredibly heavy compared to the conventional flywheel.

A replacement cost next time, as a conventional three part clutch kit, will be 1/4 of the cost.

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The DMF, as someone else pointed out, does not have any kind of centrifugal clutch, it's just one flywheel connected to another through a spring / damper to reduce transmitted vibration. I doubt that changing for a normal one would make any difference to, nor damage the engine since that's where the vibration is coming from. The DMF stops some of it being transmitted to the gearbox.

It could cause an improvement in MPG as the vibration is causing the flywheel and transmission to be accelerated and decelerated a little as it vibrates. This turns in to noise and heat, lowering the transmission efficiency. I doubt it will make that much difference though on an already thirsty engine.

I had a look at a Rakeway DMF fitted to a Defender. I was certainly more noisy at low RPM - but didn't seem to make much difference higher up the rev band.

There is a good description of how they work here: http://forums.quattroworld.com/s4s6/msgs/24536.phtml

The most common failure on Land Rovers seems to be the dampers. This changes the resonant frequency of the system and allows more vibration to be transmitted. It also allows the flywheel to resonate at certain frequencies (rpm) which can cause the friction plate to break traction with the pressure plate and allows the clutch to slip at certain engine RPM's.

When I change mine - it will be for a single mass type!

Si

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The driven plate on a clutch conventionally has springs in the centre to transmit the drive and absorb the shock loadings.

On the clutch I had removed the driven plate was solid.

That leads me to suspect that the whole DMF idea is to move the shock absorbing springs from the driven plate tot he flywheel so that the flywheel becomes a consumable service item, an expensive solution to a problem that had already been previously solved by cheaper means.

This increases the cost of parts and labour so increases profits for the motor industry.

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