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Dual Mass Flywheels For Dummies by William

Should start out with this having no affiliation with the for dummies series, but when it comes to these things, we all seem to be a bunch of dummies. I’d like to state that I do not 100% know what is going on in this design of failure, so this will mostly be speculation on my part, or for anyone who helps with information or idea’s on what is why or how.

dmf_800 dmf_801

This is the dual mass flywheel. Pardon my rust, but that’s what metal does.  The dual mass flywheel is supposedly two flywheels mated together with some springs as you can see in the picture on the right. Let’s dig inside and see how this thing really works.

dmf_1000 Lets get these bolts loose on the top here first, they are the most obvious piece to the puzzle. Almost everything else appears to be rivets except for the two allen screws on the bottom of the DMF. I had to use the impact to bust these things loose, and boy were they on their tight. I do not really think you would want it coming apart.


dmf_1002 This is the bottom side of the surface that I just unbolted. You can see that it is balanced before assembly. This is the main piece of the clutch that mates up with the clutch surface. The odd thing that I noticed is that the center ring there is very shiny.



dmf_1001 On the center ring here where that shiny surface mated, it was a weird texture. Reminded me of a brake pad or a clutch style material. Lets take a closer look.




dmf_1006 dmf_1007

I used a screw driver and a hammer to try and chip the surface away. Best I can tell is that this is some sort of clutch style material. This was surely an interesting find.

dmf_1003 dmf_1004

in these two pictures we can see one of the main reasons of failure in the DMF. You can see these little pieces of what look like metal inside there. I believe they are the main cause of the flywheel becoming unbalanced. They just float around there with no place to go.

dmf_1005 This is a picture of the the part that is between the springs. This whole ring is held down with some rivets in one large piece, you can see one of the hold down rivets at the top of the picture.



dmf_1008 dmf_1009

I decided to drill the rivets out and press on. After finding the right size and spending a good hour drilling these things out I made some progress.

dmf_1010 dmf_1011

I used a screw driver and a hammer and had to work my way around the ring to get it popped free. even with the rivets drilled out, it still came off pretty tough. The picture on the right shows the reverse side of the ring.

dmf_1012 I set the ring on top of the other piece to show how it would look with the mating surface on the flywheel.





dmf_1013 dmf_1014

Here are some pictures of the springs and the setup without the ring on the assembly.

dmf_1015 dmf_1016

Here you can see the main cause of the problems with the DMF. The whole center of the flywheel moves and allows this slop between the springs.

dmf_1017 As you can see here with the spring out, there is 2 bushings that hold the spring in place and are a buffer between the metal. I’m not sure what the material in the center is, but you can see how the end piece broke off on the one bushing, that is what we seen rolling around in the spring earlier.


dmf_1018 With all the springs out, you can get a better view of the assembly, there are more plates further in it appears, just like this plate we see on the top.




dmf_1019 This is the reverse side of that top plate there. I’m not sure what is up with why this looks like this.





dmf_1020 dmf_1021
You can see there are some copper rings in here that are angled to provide some sort of spring action to the pack. I don’t know if they were compressed or not when I drilled the rivets out and removed the top ring. Hard telling.



dmf_1023 dmf_1024

Here is a close up of the rubber pieces on the ring that holds the springs in. You can see they wear as well. I want to say the metal by them wears also, but I did no do any measuring to compare them.

dmf_1025 The bottom of the ring here you can see there is more of the clutch material like the other ring. So, we got two identical rings with some springs in the middle pressing them out too two identical plates riveted to the the second part of the flywheel with clutch material on the inner ring to prevent slippage or some sort of resistance against pressure on the springs.


dmf_1026 dmf_1027

That leaves us with this center hub here. I used a rubber piece to show you that this is indeed a bearing pack.

dmf_1028 On the back side of this part of the flywheel, as I mentioned before, there are two allen screws. They were remarkably easy to take out also.




dmf_1029 dmf_1030

Flipping the flywheel back over and pulling away the bearing hub you can see more clutch style material on the back of the ring on the bearing and a piece of plastic with notches in it. Wait, what plastic? You can see the hub is keyed to the plastic ring. I do not fully understand what this does.

dmf_1031 dmf_1032

The piece of clutch material comes off, with tight tolerances. I had to influence it off a bit, but no hammer was required. You can see there are more rings inside that assembly, which I’m guessing the plastic ring keeps in place. The right ring is a copper ring like the other copper rings with an angle to it for some spring action, and the other ring to the left is really flimsy like a piece of tin.

dmf_1033While I was turning the bearing unit, I did not feel any resistance from the clutch materials on any of the pieces. The only resistance in the hub here was from the flywheel making its short rotations causing some grooving in the race and cups inside physically resisting my turning of the hub while I tried to rotate it. It smoothed out some after a few turns, but you could feel the bearing damage inside. You can see the pilot bearing in this picture is rusted really good as well. It looks like this is the main piece of the Flywheel. Its really a three or maybe even a four piece flywheel, not a 2 piece like everyone has though. Everything stems off this piece here which is held in by the 2 allen screws, then all the other parts are clamped down around it by rivets and springs.

I’m going to toss in the remaining break down pictures in bulk here for you to look around on. I tried to keep like parts from the order they came off together in some sort of break out format.

dmf_1034 dmf_1035

dmf_1036 dmf_1037

dmf_1038 dmf_1039

dmf_1040 This is the part where I’m going to throw in large amounts of speculation on the post. Most were educated guesses based upon observations so far.

I believe the main failures of these flywheels has to do with the clutches failing inside the unit. The springs at there to snap it back into place after putting torque on the motor, but eventually wear, or get dirty and stop resisting the pressure allowing more free travel in the clutch resulting in worn bushings for the springs. This eventually worsens as time goes on and more miles are put on the clutch, or more stress would be a better explanation allowing them to damage themselves. The clutches do not resist the turning of the flywheel when you have it out of the truck, the main plate feels as though it is free spinning until it touches a spring pack, there was no resistance in mine.

I really do welcome all suggestions or thoughts regarding this and my explanations. Please be detailed in your comments and reference the picture number you are referring too if you are talking about a picture.

Please also remember, I do not really know anything about these devices or their intended performance, only that it is designed to reduce vibrations.


Anonymous said...

Thanks for your time & effort to dismantle this DMF.What they meant by Dual Mass are the 2-pieces(the big plate you first removed & the later 1 with all the teeth(ring gear))...it's not the number of sections.From what I can see is it works like a cross between a Clutch & the clutches in a A/T.

The springs work like the springs you see in OEM type clutch.It's designed to take up the shock during clutch engagement. The clutch material you chipped off ,copper rings & those rings with clutch material on them also act to smooth out the clutch engagement much like the clutch packs in a A/T.

Now I know why these DMF are $O $$$.Look at all those pieces.A DMF is designed to smooth out clutch engagement.If you don't mine rattles, lack of smooth engagement or are racing then replace the DMF with a Solid or lighten flywheel.

Anonymous said...

Hi, My flywheel looks OK, Except some of the center ball bearings seem to be missing. There are 28 bearings left. Do you have a count on how many there should be? Also do you have any idea as how I would lose the rest. Also, how could I replace/install the missing bearings. Any ideas? Thanks, Lorne 915 581-7709

William said...

Lorne, If you have any bearings missing, or any excess play or vibration in the DMF, you will want to replace it ASAP. DMF's are expensive, and you'll end up with the same problem later on, going with a whole new clutch will be the best bet. The DMF Clutch and PP will not work on a solid flywheel unfortunately. Valair or South-Bend are going to be one of the best solutions to go with. I deal with Valair personally.

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