Buzzin' Flywheels!!! - Page 2 - PeachParts Mercedes-Benz Forum

t walgamuth · #16 02-28-2010, 09:41 AM

I have the 38# genuine oem 300d fw. If I shift to fourth at less than 35 mph (with a 307 diff) it will buzz very strongly, and I cannot use fifth at less than 45. It does not seem like a problem, though the engine would pull at a lower rpm without complaint other than the buzzing.

OM616 · #17 02-28-2010, 02:26 PM

It would be interesting to see a picture of the AUTO weight mentioned.

I converted my 300D to a 4-speed I do not remember seeing anything on the tail end that was different than the manual trans. There was only a triangle flange.

I had a thought of modifying a small block harmonic balancer to go on the out put shaft, but there is no room.

I have also contemplated casting a weight and bolting it to the case as close to the tail as I can to change the natural frequency of the assembly. Chevy did that on some of there cars back in the day.

t walgamuth · #18 02-28-2010, 07:07 PM

I had a damper that came on the 300d euro and we left it off when swapping the five speed into it. It saved me having to have a driveshaft made up. I wonder if that has contributed to buzzing?

rcounts · #19 02-28-2010, 10:15 PM

Au contraire my friend I DO understand how resonance works. I also understand second and third order harmonic resonance. i.e. if an object has a resonant frequency of 200 RPMs (as in our driveshaft example) it will virtually always have a second and even third resonant frequency that is a multiple of the first resonant frequency. In other words if it is a true resonant frequency issue at 200 RPMs it will also exist at some multiple of 200 RPMs (400 RPMs, 600 RPMs, 800 RPMs etc.)

I also understand that at the higher resonant frequencies the resonance is much more destructive - due to the increased energy level. Hence my comment about it tearing itself apart at higher RPMs (if it were a driveshaft resonance issue. Read your own Wiki reference and follow the link to the story of Galloping Gertie (which was located about 20 miles from where I live.

The lack of direct connection to the engine in the automatic tranny example doesn't hold water either. The rotation of the driveshaft is the same whether direct coupled or hydraulic. Unless you're saying that the engine vibrations are the source of the resonance in the driveshaft - in which case the heavier flywheel would help dampen the vibrations on the other end - much like the pendulum dampers mentioned in your Wiki article.

I think you may need to read a bit more than one Wiki article to fully understand the subject of resonance.

I also think you need to learn how to "talk" (or otherwise communicate) to people - so you don't end up just like your hero Lance...

crashone · #20 02-28-2010, 10:48 PM

I got the part number today while I was adjusting a shift rod. I can't find a source for this part so if someone here knows where to search here it is: 126 411 02 47 318. I would like to know what you come up with. Thanks.

Eric · #21 03-01-2010, 07:06 AM

Quote:

Originally Posted by rcounts

Au contraire my friend I DO understand how resonance works.

Based on your last post, that much is definitely not true.

Quote:

In other words if it is a true resonant frequency issue at 200 RPMs it will also exist at some multiple of 200 RPMs (400 RPMs, 600 RPMs, 800 RPMs etc.)

The resonation is not rotational RPM based, its the pulsation of the engine's combustion at a specific RPM range.

Quote:

Unless you're saying that the engine vibrations are the source of the resonance in the driveshaft - in which case the heavier flywheel would help dampen the vibrations on the other end - much like the pendulum dampers mentioned in your Wiki article.

Post #16 clearly disproves this idea.

Quote:

The lack of direct connection to the engine in the automatic tranny example doesn't hold water either.

Actually it does, a fluid coupling is an excellent damper.

R Leo · #22 03-01-2010, 10:49 AM

This is beginning to sound like the Open Discussion area...you guys need to keep it on topic and between the white lines of civility.

FWIW, the buzzing isn't the flywheel, it's the engine's power impulses. I can rev my engine in neutral to 3500+RPM and there's no vibration with a 616 flywheel. I've been into a lot of these cars that were auto-equipped and never seen one of the driveline dampers you mention. I know they exist but just not on the cars I have worked on.

rcounts · #23 03-01-2010, 11:10 AM

OK Eric, now we're getting closer to being on the same page. So you're saying it is an engine harmonic, being transmitted through the transmission to the driveline, and the damper on the driveline works to supress it? See how much better this works when you communicate your ideas instead of spitting out acidic little one-liners? You're obviously a smart guy, and know a lot, and when you actually communicate that knowledge it can benefit us all...

So then, if what you're saying is true, I can put the 4-speed and flywheel from a 240D into my 300D, and all I have to do is put the driveline damper from a 300D automatic on between the transmission and the driveline, and I'll have no vibration problems at any RPM range? Crashone, does that describe what you've done? And does it eliminate ALL vibrations at ALL RPMs? If not maybe you need the heavier flywheel as well as the damper. After re-reading t walgamuth's post, (#16) I see that the 300D flywheel alone isn't doing the trick by itself for him. Maybe the secret is to have BOTH.

After additional pondering, I see where although the heavy flywheel from the AX-15 seems to be doing the trick for vlado in the transplanted OM617 in this Jeep, the other variables are also completely different (different tranny, different driveshaft, different everything).

lutzTD · #24 03-01-2010, 11:54 AM

my two cents after about a year and half with 4spd in my coupe

my setup. 617 turbo, 4spd manual, 240D flywheel, 2.47 450sel rear end. 240auto crossmember, custom cut driveshaft, 300SDL driveshaft dampner.

at first I vibrated so bad I could not drive it

after many trials I found that spacing the crossmember down by 3/8 removed all vibes but the sub 1800 rpm 3rd and fourth vibes

added 300SDL damper, no change

added 2.47 450SEL rear, major improvement but still annoying, I believe this also changed the driveline angle slightly but it may also have been the rag joints were new

blew the 4spd, replaced with another PNP unit. vibes GONE. I ruitinely drive in 3rd or fourth at 1500 RPM with very minor vibes, not annoying at all, but I can hear them

if you havent, try spacing the crossmember down, also check your trans, mine blew the 3-4 gearset which was also causing the majority of my vibrations.

I have a true 300D flywheel, but never installed it becuase the 240D unit in mine is working flawlessly.

JB3 · #25 03-01-2010, 12:16 PM

Im working on another swap right now as well, and Id like to add this damper up front. Im thinking of using this one off of a 190E, would it be worth finding one off of a 300SDL, are they a lot heavier?

I noticed the same vibration at low RPMs on my first 4-speed conversion, but I quickly forgot about it, and put 30-40 thousand on it with that problem. I have a lead foot, so it may be that I was never driving at a low enough RPM and shifting high.

Id like to eliminate it though, I think I will try adding the weight to the flywheel and adding this 190 damper since im right at that point anyway. Might as well do both since earlier in the thread both together have been credited with knocking this issue on the head.

Would the weight added to the flywheel be best added around the outside, or on the face where the material has been drilled out? Whats the stock weight of the 240 flywheel, is it 28 lbs?

Heres a pic of the damper I have available-

lutzTD · #26 03-01-2010, 12:19 PM

Quote:

Originally Posted by dropnosky

Im working on another swap right now as well, and Id like to add this damper up front. Im thinking of using this one off of a 190E, would it be worth finding one off of a 300SDL, are they a lot heavier?

I noticed the same vibration at low RPMs on my first 4-speed conversion, but I quickly forgot about it, and put 30-40 thousand on it with that problem. I have a lead foot, so it may be that I was never driving at a low enough RPM and shifting high.

Id like to eliminate it though, I think I will try adding the weight to the flywheel and adding this 190 damper since im right at that point anyway. Might as well do both since earlier in the thread both together have been credited with knocking this issue on the head.

Would the weight added to the flywheel be best added around the outside, or on the face where the material has been drilled out? Whats the stock weight of the 240 flywheel, is it 28 lbs?

Heres a pic of the damper I have available-

your asking for trouble to modify a flywheel. at 3000 RPM if that thing comes apart it could take you with it, pieces will be travelling over 100MPH

I had to do some modification to get the 300SDL weight to work. If Im ever in there again I will remove it.

rcounts · #27 03-01-2010, 12:29 PM

Quote:

Originally Posted by lutzTD

your asking for trouble to modify a flywheel. at 3000 RPM if that thing comes apart it could take you with it, pieces will be travelling over 100MPH

Agreed. Its one thing to modify a flywheel to fit, totally another to try to add weight to one...

rcounts · #28 03-01-2010, 12:44 PM

Quote:

Originally Posted by lutzTD

my two cents after about a year and half with 4spd in my coupe

my setup. 617 turbo, 4spd manual, 240D flywheel, 2.47 450sel rear end. 240auto crossmember, custom cut driveshaft, 300SDL driveshaft dampner.

at first I vibrated so bad I could not drive it

after many trials I found that spacing the crossmember down by 3/8 removed all vibes but the sub 1800 rpm 3rd and fourth vibes

added 300SDL damper, no change

added 2.47 450SEL rear, major improvement but still annoying, I believe this also changed the driveline angle slightly but it may also have been the rag joints were new

blew the 4spd, replaced with another PNP unit. vibes GONE. I ruitinely drive in 3rd or fourth at 1500 RPM with very minor vibes, not annoying at all, but I can hear them

if you havent, try spacing the crossmember down, also check your trans, mine blew the 3-4 gearset which was also causing the majority of my vibrations.

I have a true 300D flywheel, but never installed it becuase the 240D unit in mine is working flawlessly.

This is a common problem and solution from the Jeep world. When the output shaft of the transmission and pinion shaft of the differential are not parallel it creates a problem.

As a flexible joint which is operating at an angle rotates, the shafts rotate a little bit faster during some parts of the rotation, and a little slower during other parts of the rotation. If the universal/flex joints are at different angles (tranny output and pinion input shafts nor parallel) then these speed fluctuations at the opposite ends of the driveshaft don't match up (get out of phase). This can cause a serious driveline vibe.

By spacing the crossmember down, you are pointing the rear of the transmission down and changing the angle of the output shaft to more closely align with the pinion input shaft. That eliminates the out of phase issue and dramatically reduces vibrations.

lutzTD · #29 03-01-2010, 01:39 PM

Quote:

Originally Posted by rcounts

This is a common problem and solution from the Jeep world. When the output shaft of the transmission and pinion shaft of the differential are not parallel it creates a problem.

As a flexible joint which is operating at an angle rotates, the shafts rotate a little bit faster during some parts of the rotation, and a little slower during other parts of the rotation. If the universal/flex joints are at different angles (tranny output and pinion input shafts nor parallel) then these speed fluctuations at the opposite ends of the driveshaft don't match up (get out of phase). This can cause a serious driveline vibe.

By spacing the crossmember down, you are pointing the rear of the transmission down and changing the angle of the output shaft to more closely align with the pinion input shaft. That eliminates the out of phase issue and dramatically reduces vibrations.

agreed, but I think it also illustrates that some of the vibe problems are not engine related as much as driveline geometry related or transmission condition related. I just dont feel a 300D flywheel is the complete answer. I am perfectly happy with mine, if I ever put in my 5 speed I will use the 300D flywheel, but for now it is just sitting in the garage.

JB3 · #30 03-01-2010, 01:42 PM

Quote:

Originally Posted by rcounts

Agreed. Its one thing to modify a flywheel to fit, totally another to try to add weight to one...

should not be a bad job or a problem safety wise, just process and cost involved. I was first thinking about having a ring cut that matches the exterior ring of the flywheel with either water jet or laser cut out of 1/4 inch steel, then welding all the way around and having it all reblanced and cut for true at a machine shop. It would add to the thickness, which was my question, how thick is too thick?
One ring of 1/4 inch would probably not weigh more than 2 lbs, so that might not be an effective method. To do rings all the way to make up 10 lbs might make the thing so deep it would touch the bell housing.

It would be a lot harder to professionally add weight to the exterior of the flywheel.