Dual Mass Rattles at shutdown, etc

[MicahO]

So the new car has a dual mass flywheel - most (all?) BMW's do. The dual mass serves a good purpose, as I have been reading. It's sprung nature prevents engine power pulses from actually reaching into the transmission and causing gear rattle or gear lash. This is good.

But why then do BMW dual mass flys all make noise when the car is turned off, and sometimes even when simply declutching at low engine and road speed? Is it just the sping mechanism taking up the slack and clicking a little? Should we just hear that and say "Well, I'm sure glad that's not my GEARS clashing!"

Thanks for the input!

(and no, I'm not thinking about swapping the fly/clutch in the new car. Yet. ;) But after a DSC-defeated, 'slightly' tail-out, single-tire-smoking power-almost-slide last night, the $2600 LSD sounds pretty good......)

--Micah

[Bill R.]

http://www.bimmernut.com/%7Ebillr/images/dualmass-1.jpg
So the new car has a dual mass flywheel - most (all?) BMW's do. The dual mass serves a good purpose, as I have been reading. It's sprung nature prevents engine power pulses from actually reaching into the transmission and causing gear rattle or gear lash. This is good.

But why then do BMW dual mass flys all make noise when the car is turned off, and sometimes even when simply declutching at low engine and road speed? Is it just the sping mechanism taking up the slack and clicking a little? Should we just hear that and say "Well, I'm sure glad that's not my GEARS clashing!"

Thanks for the input!

(and no, I'm not thinking about swapping the fly/clutch in the new car. Yet. ;) But after a DSC-defeated, 'slightly' tail-out, single-tire-smoking power-almost-slide last night, the $2600 LSD sounds pretty good......)

--Micah

[MicahO]

Now dangit - I'm sitting here digging in the old TIS, the 6/2000 TIS, and you know where I got it, and I've looked under my e34 BF10054, and I've looked under the 2001 M54 330i, and I can't make that dang document come up!!!!!!

But thanks!


(again!)


(dangit.)

[MicahO]

Eeeerm. I found it. Couldn't find it for the hour I spent before my post. Or the hour between mine and yours. Found it this time. Damn TIS needs a search function.

How 'bout a smilie for one's tail between one's legs?

:)

[Bill R.]

can't find... fortunately the flywheel was one i had saved in the photo space that Ed provided for me... Thanks Ed... So now I just have to remember to look through every image there first... Why didn't i pick better names for them?






Eeeerm. I found it. Couldn't find it for the hour I spent before my post. Or the hour between mine and yours. Found it this time. Damn TIS needs a search function.

How 'bout a smilie for one's tail between one's legs?

:)

[Jeff N.]

Aw heck...just stick the ubiquitous E28 flywheel in there! :)

[MicahO]

It's funny being around the e46 boards - there aren't a hell of a lot of people who know the cars like we know our e34's. Of course, they haven't had to get to know them like we have. But questions about the location of the parking brake and what's that (flywheel) rattle are pretty normal. I'm glad I don't have to work on my car for a while, but I really like knowing what's going on in there......

[Jeff N.]

..that's ridiculous...

[MicahO]

Yeah - I know.... On the e46, all of them except the mighty M3, the diffy is in a new case that has no room for an LSD. Brett Anderson can hand build one for me for $2650. Turner sells "e46 racing diffs" for ~$4500 each. Dan at diffsonline.com will custom build one with Kaz internals for somewhere in the $2800 range, but it's got to be a 3.15 or higher due to the size of the ring gear and spacing in that little case.

Other diffs don't fit in the space provided. I've actually already bought another 3.07 slip from a guy how upgraded his ZHP to a 3.38 slip. But I really don't think I want to spend that money. Well, today I don't think I do. Who knows what tomorrow will bring.

They try to sell the DSC as "LSD-like behavior." NOT!

[George M]

There is no escape.
:p
George
Typical refrain on the E-46 board: Guys...check out my phat cup holder. ;)

[MicahO]

You know how it is with BMW's - learn or die!

(Where to die is to find oneself in a Camry ;) )

We've just all evolved to be much more 'resourceful' due to the age of our systems.

[George M]

exactly...learn or die...lol I was just teasing of course. Issues abound with any model...must be some freedom in the localized masses on the flywheel to give it the death rattle as with the old E-34...remarkable that hasn't been fully addressed....a matter of chasing noise frequency around...where do you want it to rattle in other words...cause its gonna rattle some place.
I love the new 330i...would be my choice if I bought a new one.
George