gear box noise after engine shut down

Voith visco-elastic bimass flywheel. How are your hot starts?

 

Bingo!!

Very common on 355's. Basicly the flywheel needs to be disassembled, cleaned, inspected,and repacked with the correct grease. Not a hard job to do but does require a special too to remove it form the carrier housing.

 

What can happen if left unattended. I also have a noise on shutdown in neutral, but it sounds like a slight grinding against the ring gear (ringing it like a bell). It lasts for a brief instant, maybe less than 1/4 second. Does this seem like the same noise?

 

If a failing dual mass flywheel is left unattended the phenolic parts inside the flywheel can melt, meaning replacement rather than rebuild. Several people on this list have rebuilt thiers. My (348) flywheel cost me less than $100 to rebuild at home. Most of the cost was just Kluber Grease and the triple seals on the input shaft. I'm not sure about the F355, but on the 348 (similar), if you let it go and have to actually replace the flywheel it is a pretty expensive proposition.

 

Shan is 100% correct. The peices that are inside the flywheel are not available seperately. If you catch it fast enough, no real damage will be done to the internal components, and you can just clean and repack it.

 

I've heard this noise on alot of 355s. I don't think most people even know its a problem. If I depress the clutch at shutdown, does this prevent damage?

Cheers
Ade

 

In laymans, can anyone tell me how and why the 355 flywheel works as opposed to the standard solid fly wheel with fitted ring gear. How does it work??

 

In Layman's terms -- no -- but this is an interesting presentation:

http://www.luk.de/Bibliothek/Download/folien_zms.pdf

Essentially, the dual-mass flywheel adds a spring and damper function in-between the crankshaft assembly and the clutch/driveline assembly that helps reduce ("smooth out") the "vibrations" (the angular acceleration impulses from the power stroke events) transmitted into the driveline.

(Very much like how a spring and damper is placed in-between the wheel assy and the chassis to reduce the vibrations/impulses that are transmitted from the wheel to the chassis.)

 

Wasn't quick enough to edit my previous post, but see page 9 of 28 in that .pdf file which shows how the vibration (i.e., the angular acceleration) is reduced in the transmission with the dual-mass flywheel (while it actually increases the vibration/angular acceleration of the crankshaft itself -- but the occupants don't feel that).

I believe this is more of an issue for diesel engines which have a more violent power stroke. Also interesting to note that in almost every application of this technology people b*tch about the added complexity and a single-mass retrofit seems available.

 

A few days ago I talked with the main dealer about this same issue. An exceptionally well informed tech. told me not to worry about it. It was the dual mass fly-wheel, and it's intention was to smoothe out the acceleration. He said you could also often hear it if you took off slowly in a too high a gear.

Also, he mentioned something else which I can't fully recall ... a valve back there (maybe a ball valve) .. that if worn would create a similar rattle.

 

It's all good and well to say "Don't worry about it" in the sense that it won't cause your engine to blow up, or other disasters. But while the flywheel is rattling away due to lack of grease, the internal parts are gradually wearing out, those internal parts are not available for replacement, and the clutch disc is soaking up the grease. As mentioned above, repacking and resealing the flywheel can be done before the flywheel becomes "toast". A new flywheel is what, $3000????

 

Not to mention the entire thing WILL catch fire! I have seen it personaly on a 348. The dude kept driving with grease flying around and it caught fire one day at a stop light.

 

Not that I'm doubting you for a second, but wouldn't that create a horrendous amount of stink and smoke before it caught fire? Seems like the driver would have to be REALLY insensitive to let that happen.

 

Does this flywheel noise & problem ever happen on the F-1 transmission??

Dino

 

If you can't take the word of a qualified main dealer technician ... what do you do?

Maybe he listened and thought it was the beginning stages of deterioration that could be fixed at a more opportune moment. The car had its 30k not 1000 miles ago, during which the clutch etc is always inspected and replaced if needed.

As for the 348 than went up in smoke ... the guy must have ignored a serious amount of tell-tale smoke or stink.

If the 355 clutch is repacked etc ... how long before it starts rattling again?

Anybody?

 

FYI. I tried this out, and if you depress the clutch at shutdown this avoids the noise completely... good trick if you don't want to hear the noise.
Ade

 

Ken,

I got the technology to do this. I'll be trying my solid set-up Friday and let you know how it goes. I gutted the internals and "fixed" the parts then rebalance them. I have lathes and welders and such. I'm also lighter now so I expect faster spinup and launch out of turns.

 

Here's some pics from the 348 dual mass flywheel. the rattle is a tell tale sign of impending failure, then you start having hot start problems. As far as I can tell this was more of a problem for th e348's than the 355's.

Does any body know why?

 

Here's one with the right color grease that hasn't been discolored by gear oil.

 

BillyBob!!!! Right on bro. Give me a call and let me know how it goes. I still have my old flywheel. The kid that was gonna buy it from me never called me back. So it is waiting patiently in my garage to get modified. MAN I hope it works. I bet you even gain a few ponies.

 

Question .... impending dual mass clutch failure is then followed by hot start problems.

What's the connection between the clutch and 'hot' starts?

Regards.

Pete

 

Pete,

i'm not sure what you mean about the clutch question. But the clutch is right in front of the Flywheel they are packaged as a unit. Usually what causes these FWs to go are the seals between the output shafts coming out of the tranny deteriorate and let gear oil through and into the FW. Some with hot start problems have found that if you hold in the clutch at start up you can eliminate the hot start problem. Eventually you have to fix it. when doing the clutch it is probably best to inspect the FW, which is not hard to do, especially if you have noticed some oil or grease inside of the FW/clutch housing.