Manual Conversion Vibration

[diesel don]

Hey Everyone:

Upon converting an '82 240D (Manual) to an upgraded 300D-T, we have most of the bugs worked out. She fires instantly and runs out nicely. However, we have one issue that we can't figure out.
At idle and upon take off, there is a rather major vibration. It almost reminds me of one of my other MB's that had a driver's side engine mount missing. The car would vibrate the heck out of you until the rpm's were sufficient to lift the engine off the frame.

1. I did not balance the flywheel because I couldn't find any marks. However, wouldn't this affect vibration at all rpm's? After 1500 rpm's, the car runs out smoothly.

2. I have new motor mounts

3. I had to fabricate/adjust the former crossmember holding the tranny mount. I drilled holes 1" narrower. In the end, this mount might be 1/2 to 1" higher (closer to the bottom of the car) than it was.

Any thoughts?

Thanks, Don

[R Leo]

Originally posted by diesel don

Upon converting an '82 240D (Manual) to an upgraded 300D-T, we have most of the bugs worked out. She fires instantly and runs out nicely. However, we have one issue that we can't figure out.
At idle and upon take off, there is a rather major vibration. It almost reminds me of one of my other MB's that had a driver's side engine mount missing. The car would vibrate the heck out of you until the rpm's were sufficient to lift the engine off the frame.

1. I did not balance the flywheel because I couldn't find any marks. However, wouldn't this affect vibration at all rpm's? After 1500 rpm's, the car runs out smoothly.
The harmonics of the motor mounts and the mass of the engine may be such that the vibration is masked at higher RPMs. IMHO, you need to pull that tranny and flywheel, find those marks and reassemble. See this thread for a pic of the flywheel mark; it was hard to spot on this particular flywheel becasue it was obscured by a lot of clutch dust: http://www.peachparts.com/shopforum/showthread.php?s=&threadid=77924

2. I have new motor mounts
Great, at least you know it isn't the mounts!

3. I had to fabricate/adjust the former crossmember holding the tranny mount. I drilled holes 1" narrower. In the end, this mount might be 1/2 to 1" higher (closer to the bottom of the car) than it was.
Not the source of your vibration unless the transmission is actually touching the body somewhere. But, this sounds like you'll eventually have a driveline problem. The flex disks aren't intended to function as a universal and any misalignment through the disk will result in driveline vibration and premature failure of the disk. Raising the back of the transmission that much will cause a misalignment issue.

[leathermang]

Did you use a 240 flywheel or a 300 ?

[diesel don]

Leathermang:
I used a 300 flywheel from a 300D euro manual 4 speed.

R Leo:
To say that the vibration is masked at higher rpm's seems strange to me as it goes from monster vibration to regular smooth. It is not a gradual type of deal. Its almost like something removes itself from the frame.
To think of yanking that stuff again when I studied it for marks would drive me crazy. There were others that stated that they've found units that are unmarked. Have you ever seen that or am I dreaming?

I do notice that the front end is lower than my other sedans. I can tell that the chassis (although a 123) is weighed down more by the 300D. Perhaps the springs?

Don

[leathermang]

Yes, you probably need the springs for the 300. MB is sorta compulsive about providing a level car. They offer different spring mounts for just about every combination of accessory ( thus weight ).
Did you do this project without the benefit of owning a Factory Shop manual for the chassis, ( two books ) and the engine (one for each engine )?
That 300 flywheel was a good find.
Have you checked the Tech Service bulletins concerning the adjustment of rough idle on older engines ? There is one for some years and you did not say which year your 300 is...

[R Leo]

Originally posted by diesel don

R Leo:
To say that the vibration is masked at higher rpm's seems strange to me as it goes from monster vibration to regular smooth. It is not a gradual type of deal. Its almost like something removes itself from the frame.
OK, more information is a good thing....there a lot of tight fit stuff under there, take a look at things like exhaust mounts, turbo heat shields etc.

To think of yanking that stuff again when I studied it for marks would drive me crazy. There were others that stated that they've found units that are unmarked. Have you ever seen that or am I dreaming?
I'd be willing to bet money there are marks on that flywheel and crank. I say this because, the Germans are absolutely anal-retentive when it comes to mechanical things and processes and I can't imagine them leaving marks off of some flywheels and putting them on others. Heck, the OM617.95X FSM even documents a mistake that they made in the timing marks on some engines. But, by all means, first look at the easy fixes mentioned above.

I do notice that the front end is lower than my other sedans. I can tell that the chassis (although a 123) is weighed down more by the 300D. Perhaps the springs?
It probably isn't the springs causing this vibration...but, Greg is onto something that you'll eventually need to address: ride height. A pair of new springs for a 300 aren't all that expensive but, if you still have the donor car, you might try them. Be sure and use a proper spring compressor!!

[leathermang]

OK,,, this is from an old mechanic.. ( me ) not an MB person...
One way a vibration could exist has to do with the way the vibration damper is made... with rubber...
I once had an engine where the outer part had rotated from the correct position... due to age/vibration....
and the stupid timing marks were ON that part of the damper...that one took me a while to figure out...
but back to the point here... if the rubber has deteriorated... then it could be ' wobbly' at low rpms..... but solid when thrown outward by centrifugal force at higher rpms...
Just a thought...
Since your vibration damper may be the same age as your engine I think with all the work you have invested to make this about the perfect car it might make sense to just but a new vibration damper on your car...
But I still suggest you check the tech bulletins first....

[diesel don]

You guys have given me some good advice here.

The strange part about this is when you stand outside the car with the hood up, the engine looks/sounds as smooth as can be at idle. You can't hear a thing. In addition, it seems strange that the engine doesn't shake back and forth because there are no engine shocks (ala, the 240 chassis).

In other words, you don't notice the vibration until you get into the car. This is what leads me to think its a frame related thing.

I had some struggle with the heat shield and yes, there are some tight fits. I'll get it up on ramps and blocks again and go piece by piece.

Regarding shop manuals? All I have is:

1. Haynes
2. The historical archieves here
3. Current help from members.
4. Local mechanic who knows these things inside and out, but I can only bug him systematically. Not all at once.

Thanks for your time

Don

[TomJ]

Don,

Here's a possibility. With mine, I have a similar problem, only in gear and when under power. Turns out it was the crossmember just kissing the trans case (when mounted crossways on the 300D body) only when under load or at idle?

Here's a pic of what I'm talking about, you can see where I machined some material off to clear the case, but it still made the noise, so under closer exam, it was one of the rubber mount holes that protrude down from the tranny rubbing the side of the member:





At first, it really did sound like engine or something coming apart. Once I machined the crossmember more and cut off the lower tranny protrusion/mount that was unused, it's smooth.

As far as the marks on the flywheel, forget about it, TWO of the flyweels I have and the one that came off the 300D DO NOT HAVE ANY MARKS ANYWHERE. This is upon boiling and almost microscopic exam. Since the 300D flywheel CERTAINLY has no align marks of any kind, I'd say it's a really good bet the 300D crank doesn't have any marks either so there's noting to align the flywheel to anyway.

You'd think if it were externally balanced or needed to be indexed to the crank, some bright person would have made the BC asymetrical or used an align pin. German engineering...., yeah..., right.

[leathermang]

You have a LOT of Mercedes cars...
More than most people....
Is there something in your religion which keeps you from acquiring some of the factory shop manuals for your car/s ?

One mistake dealing with these engines can easily cost many times the cost of a shop manual...if not in parts ... then easily in labor and spirit...I really hate doing something twice to get it right....

[Ken300D]

I happened to notice in the pictures above that the flex disk bolts are not all pointing the same way. I don't know why, or if it will even make any difference, but the MB shop manual says that all the flex disk bolts should point the same way.

The bolt heads are always on the driveshaft side and the nuts go on the "device" side, device being either the transmission or differential.

Ken300D

[Mike123]

I have not owned my 123 since new, but changed the flex disks at 125,000. The bolts in mine were installed just as they are in the pictured unit, in other words, half one way and half the other. They were installed this way on an earlier 123 I owned, and on the 116 I still own. Since I didn't any of own any of these vehicles since new, I cannot say if they came this way from the factory, but when I changed flex disks (and I did on each MB I owned) they were all installed the same way I found the original.

[diesel don]

TomJ:
Thanks for the idea. You might be on to something as I had to recreate that tranny crossmember. I'm going to comb that area really well. Thanks for the confirm on the 'lack of alignment marks'. That thing nearly drove me crazy not finding any.

Leathermang:
You make me laugh. No one has ever challenged me on 'shop manuals' before. But as you referenced religion, I have devoted my life to working with students from THE book, so why should I avoid the shop manuals when it comes to cars. You make a good point and I'll begin looking. Perhaps the collective wisdom on the board was just too handy for me.

Ken300D:
You have me thinking about the direction of the flex disc bolts. Heck, I just threw them in there the easiest way. I better re-examine that.

Thanks

Don

[leathermang]

Well, in that case perhaps you were expecting Divine Intervention.. What was that song by Janis Joplin that went " Oh, God won't you send me a Mercedes Benz..... My friends all drive Porshes ..... I must make amends....."
I consider the manuals/board relationship to be this:
These are the people who had several score of years experience manufacturing automobiles before your particular car was made...
They wrote from that vantage point. The Board Members have the advantage of hindsight as to what worked right and did not...and ways to fix things which may not be available through Mercedes. They are also more reasonable in terms of cash outlay in their thinking process since they are not making money on the fix.
When I go and read the Actual Manual.... I am impressed by the WARNINGS and the upgrades which are listed there. These are often left off the answers by members due to their orientation of detective/advise on a particular problem. Many of the items in our engines had two or three major changes to them over the life of that style engine.... and they often suggest getting the newer version rather than just replacing the broken part on our engine.
Of course the manual's are pretty dry reading.... I have not detected ANY PLOT yet.... and they certainly don't mention all the beggetting, adultery and violence of the Other Book....
They are wonderful in the COMMANDMENTS section... DO NOT do thus and so OR you will REGRET it. !
And they mean you will REGRET it RIGHT THEN... not in some future lifetime.....

[diesel don]

Greg:

You should get published. I enjoyed all the analogies to THE book.
One final question:

Where does one find these manuals? I've scoured ebay for parts a ton of times and don't recall seeing them, etc? Do you ever come across any for sale without them costing more than another MB

Don