300 turbo manual 1700-2000 RPM vibrations - PeachParts Mercedes-Benz Forum

lutzTD · #1 12-09-2008, 11:14 AM

starting a seperate post to discuss, I am pulling posts from the 5speed sale post for reference here

lutzTD · #2 12-09-2008, 11:21 AM

i think the theory of the heavier 300D flywheel is that it helps dampen vibrations. all 4spd swaps I have seen posted here with 240D flywheels have had a buzzing vibe in the 1700-2000 rpm range. those with this fixed tend to have the 300D flywheel. the other use of the heavier flywheel would be at start of motion on first clutch release it will have more rotational inertia to take off easier. I dont have any issue taking off with the 240D flywheel, even with 2.47 gears. and the buzz is easily remedied, shift at 3200 to avoid load situations at 1700-2000 rpm.

lutzTD · #3 12-09-2008, 11:22 AM

from R_Leo

Quote:
Originally Posted by lutzTD

i think the theory of the heavier 300D flywheel is that it helps dampen vibrations.

I wonder about that. A 617 has a completely different set of harmonics from the 616 and a little extra weight on the flywheel doesn't seem like it would change much. I always though the added flywheel weight is because the 617 has the additional mass of a crank throw, piston and con rod.

Quote:
and the buzz is easily remedied, shift at 3200 to avoid load situations at 1700-2000 rpm.
That's like telling someone to stop breathing to avoid getting a cold. Come drive mine that way sometime; it sux, trust me.

All that said, I've thought about the vibration long and hard and, have come up with these factish things:
1. On this forum, there are only a handful (say six or seven) of conversions to 4-speeds in turbo 617s
2. Of those, only one or two that I know of has reported NO VIBRATION in the 1700-1900 range. Case in point: Member TomJ did a several conversions for some biodiesel outfit in Colorado and all but one vibrated plus, I recall one other member that did a conversion who reported no vibrations. I don't believe there was any connection between vibration and flywheel weight in either of those situations.
3. Henry Schuman who has worked on more Mercedes-Benz that we'll ever see, once reported to me that in his career some cars he worked on would have a harmonic balancer device in the driveline, right behind the front flex disk. The balancer wasn't on all manuals but, similar models would sometimes have the balancer and sometimes not.
4. Mine vibrated with both the 4-speed and the 5-speed.

My (admittedly half-baked) conclusion is this:
The issue is a torsional oscillation in the driveshaft caused by one or more of the following:

1. The 617's power pulses are harmonic with the driveline length at certain RPM and some driveshafts amplify torsional oscillation when there are significant differences in durometer value between front and rear flex disks.

or,

2. The 617's power pulses are harmonic with the driveline length at certain RPM and amplify torsional oscillation when the durometer value of the front and rear flex disks is too high.

or,

3. The 617's power pulses are harmonic with the driveline length at certain RPM and amplify torsional oscillation when the durometer value of the front and rear flex disks is too low.

4. The harmonic balancer was installed at the factory on the cars that had a vibration because it was a faster solution than swapping out flex disks to eliminate vibration.

lutzTD · #4 12-09-2008, 11:23 AM

from MTU_Power

Quote:
Originally Posted by R Leo

Find one and go for it!

ya mean like this one?

Here's the harmonic balancer

Both are in my garage along with everything else from a 617-912 mated to a four speed. I pulled them from the yard but am looking for a car with a bad tranny to put it into.

lutzTD · #5 12-09-2008, 11:24 AM

from T Walgamuth

I've got one of each. IMHO, the heavier flywheel and the extra flywheel on the ds all are there to dampen the fierce vibrations of the 5 cyl 617.

Every 617 I have had with an automatic dances up and down like a jack in the box. My 240/300d with the proper 300d fw idles so smoothly you would swear its a six.

With a 240 fw on the 300 (I have one of those too, my 82 300cd) there is noticably more vibration but not enough to fool around trying to build up a 240 fw to match the weight of the 300 fw.

I will say this though, in climbing from one to the other the one with the 300d fw is much easier to shift smoothly. With the 240 fw its very difficult to shift smoothly. I think its because the engine speed drops too quickly.

lutzTD · #6 12-09-2008, 11:26 AM

shifting at 3200 works awesome for me, I sometimes shift at 4500. I dont think these motors are meant to be lugged. I agree there are some harmonics at play with the 617 and 4spd. I have also lowered my tranny mount with washers to get rid of most of the vibs. It got better with my rear swap to a 500SEL 2.47, nothing else changed. the shorty front drive shaft is indeed different than the 240 by about 4 inches suggesting a higher frequency harmonic potential, along with the 5 cylinder adding a cylinder at each RPM giving a pulse frequency increase. that makes sense. I have added the damper on the DS and it made no difference. if it is the DS vibrating, would adding weight to the middle of the short driveshaft be the answer to reduce the harmonic frequency?

lutzTD · #7 12-09-2008, 11:27 AM

from R_Leo

I don't think it is the short shaft because the vibration is almost the same on my 5-speed as it was on the 4-speed and the 5-speed's shaft is even shorter!

Interesting in your case that the damper (the thing I called a harmonic balancer) didn't have any effect on the vibration...so much for my theory.

lutzTD · #8 12-09-2008, 11:27 AM

from your comment above, I think you should try spacing the trans mount down some. before i did that mine was unbearable, now it revs to 4500 smooth as silk, 3200 shifts are nothing.

Bajaman · #9 12-09-2008, 01:04 PM

This is a little difficult to follow (who said what), but I'll add my two cents. When I first did the swap, I had the normal vibration (1700-2000rpm) in 3rd and 4th. I tried lowering the rear x-member, I now have the proper x-member. Neither substantially affected the vibration. NOW, I have increased the output of the motor considerably with the addition of a VNT turbo. I have also put in SD265 nozzles and adjusted the timing to 26*. With all of these mods, I now have 'bucking'. This can occur anywhere from idle to 2000rpm. This is low frequency say ~1Hz, and only occurs under light load. I have been contemplating adding weight to the flywheel, as it is becoming unbearable. I agree that the flywheel mass is definitely a factor and I will try adding ~20lbs when I can get a flywheel.

lutzTD · #10 12-09-2008, 02:35 PM

Quote:

Originally Posted by Bajaman

This is a little difficult to follow (who said what), but I'll add my two cents. When I first did the swap, I had the normal vibration (1700-2000rpm) in 3rd and 4th. I tried lowering the rear x-member, I now have the proper x-member. Neither substantially affected the vibration. NOW, I have increased the output of the motor considerably with the addition of a VNT turbo. I have also put in SD265 nozzles and adjusted the timing to 26*. With all of these mods, I now have 'bucking'. This can occur anywhere from idle to 2000rpm. This is low frequency say ~1Hz, and only occurs under light load. I have been contemplating adding weight to the flywheel, as it is becoming unbearable. I agree that the flywheel mass is definitely a factor and I will try adding ~20lbs when I can get a flywheel.

sorry about the hard to follow part.

how are you planning to add weight? Is it a matter of bolting on a ring to the 240D unit.

In the end, what is the availablity and cost of a factory 300D manual flywheel?

Bajaman · #11 12-09-2008, 05:00 PM

Quote:

how are you planning to add weight? Is it a matter of bolting on a ring to the 240D unit

essentially, yes. As I understand it, the difference in dimension is basically a ring around the outer portion of the flywheel. The 617 flywheel is thicker in this region. I will try to track one down next time I'm in the junk yard.

Stevo · #12 12-09-2008, 05:23 PM

Quote:

Originally Posted by lutzTD

sorry about the hard to follow part.

how are you planning to add weight? Is it a matter of bolting on a ring to the 240D unit.

In the end, what is the availablity and cost of a factory 300D manual flywheel?

Yah, I knew someone would mention that someday

, 20# would be interesting.

lutzTD · #13 12-09-2008, 05:30 PM

Quote:

Originally Posted by Bajaman

I agree that the flywheel mass is definitely a factor and I will try adding ~20lbs when I can get a flywheel.

this is giving me a bug in my ear. I sent MTUpower a PM to see if he will measure his to see what the difference is. You're right, I dont see why if done properly an added weight would not work.

MTUpower · #14 12-09-2008, 09:38 PM

Quote:

Originally Posted by lutzTD

this is giving me a bug in my ear. I sent MTUpower a PM to see if he will measure his to see what the difference is. You're right, I dont see why if done properly an added weight would not work.

I have nothing to compare it too, but tell me (with pics if you can) what to measure and I'll get right back to you.