Not so good results from 4spd swap - PeachParts Mercedes-Benz Forum

Bajaman · #1 03-18-2008, 12:22 PM

It seems that everything that could go wrong went wrong. I had a lot of headachss. One of the biggest was that the driveline was too long. I had mine made to the same length as Gavin in his CD which was a 1/4" shorter than the length posted by Rleo. Anyway, I got it in but I had to move the engine forward to get the centering bushing on its spindle then move the engine back. This was about 1/2" So the driveshaft "fits" but not very well.

The main problem is... You got it vibration. I was a little afraid of what I might find when I did this swap. The main thing that had me worried, it that fact that I DID NOT index the auto flywheel when I rebuilt the engine two years ago due to my retarded nature

Though the engine seemed to run fine without any noticeable vibration with the auto, I'm beginning to wonder if that had anything to do with the incurable hot idle shake? But, I digress. The point is I did not have a reference for the new flywheel, So I just put it on the way I had indexed the auto flywheel with the drilled out portions in the same locations.

So I drove the beast home from my buddies garage last night. Everything works great, but I've got a bad vibration at about 1600 rpm most noticeable in 4th though It will do in in the driveway if I can hold the rpm at about 1600.

This all leads me to my question: Anyone know how to use an accelerometer and an optical pickup to dynamically balance a flywheel. I can get an accelerometer for ~$30 on fleabay, and I can get Labview on my laptop easy enough, but what to use for an optical pickup for indexing the flywheel I don't know. Also I'm not real sure how to actually balance it. Would I measure the phase angle between the peak acceleration and the index from the flywheel and drill out the flywheel at the same angle physically?

Lets pool our brains and solve this problem for everyone attempting this swap

bajaman

KarTek · #2 03-18-2008, 12:53 PM

Is the vibration present around 1600 RPM regardless of the speed? If so, I'd guess the longer shaft is putting a bind on the mounts and causing the transmission of more engine vibes to the chassis.

TheDon · #3 03-18-2008, 01:03 PM

did you have the drive shaft balanced as a whole?

bgkast · #4 03-18-2008, 01:10 PM

AFAIK everybody who has done the swap has some vibration around that rpm range. The 300Ds that came with manuals in had some sort of extra disk between the flex disk and the transmission that may have been used to eliminate this vibration.

kerry · #5 03-18-2008, 02:38 PM

Quote:

Originally Posted by bgkast

AFAIK everybody who has done the swap has some vibration around that rpm range. The 300Ds that came with manuals in had some sort of extra disk between the flex disk and the transmission that may have been used to eliminate this vibration.

There are pictures somewhere on the forum of those extra large balancing discs attached to a driveshaft.

#6 03-18-2008, 04:52 PM

Quote:

Originally Posted by kerry

There are pictures somewhere on the forum of those extra large balancing discs attached to a driveshaft.

I just got one of those this weekend. And for future reference, the 300D 4-speed manual driveshaft length from tip to tip is 22-1/4 inches for the short shaft and 46" tip to tip for the long shaft (including the u-joint).

Stevo · #7 03-18-2008, 03:03 PM

Quote:

Originally Posted by bgkast

AFAIK everybody who has done the swap has some vibration around that rpm range. The 300Ds that came with manuals in had some sort of extra disk between the flex disk and the transmission that may have been used to eliminate this vibration.

I believe they did came on Euro, manual, 300Ds. A friend had one one which was discarded when he went to a 5 spd box. I have never seen one on a 240D, Euro.

Palangi · #8 03-18-2008, 09:25 PM

Quote:

Originally Posted by Stevo

I believe they did came on Euro, manual, 300Ds. A friend had one one which was discarded when he went to a 5 spd box. I have never seen one on a 240D, Euro.

My 240D had one of those balancers. The rubber was coming apart, so I took it off. No driveline vibration with or without it.

Stevo · #9 03-18-2008, 09:59 PM

Quote:

Originally Posted by Palangi

My 240D had one of those balancers. The rubber was coming apart, so I took it off. No driveline vibration with or without it.

Interesting, I wonder why they put them on Euros

The US got oil coolers but no "DF damper"

Thats OK, I can do w/o either.

MTUpower · #10 03-18-2008, 11:11 PM

You need this

Bajaman · #11 03-19-2008, 09:11 AM

Lots of good info here. I know that my driveshaft is not responsible for the bulk of the vibration as I get it in the driveway just sitting there if I rev the engine to 1600 rpm. I believe this somehow gets amplified in 4th, perhaps it resonates through the drivetrain. Anyhow, I took the flywheel off and took it and the flexplate to the machine shop to have it match balanced. I guess I will try it 12 different times if I have to in order to find the proper index.

Bajaman · #12 03-19-2008, 09:12 AM

How does that dampener attach?

peterhardie · #13 03-19-2008, 02:12 PM

...for the record, I don't have any vibration, at least none really noticeable. Lots of gear noise, some throwout bearing noise, but no vibration. Did not index my flywheel, don't have the balancer pictured earlier in this thread. Maybe I just got lucky.

I don't think you can state a fixed length for the driveshafts on conversions. If you are putting a 240 tranny into a 300, measure, measure and measure again. There are at least two different lengths of 4-speed trannys. My measurement was close but not identical to what others got for both the shafts and the shift rods.

If your driveshaft is too long, I would re-cut it. I know, $$$$, but I think you are in for problems down the road. There is a splined section that is supposed to give in two directions. That can't be good at full compression for any length of time.

Bajaman · #14 03-19-2008, 02:47 PM

Maybe I wasn't clear, the length is only a problem for getting it in. Once installed there is at least 1/2" clearance before full compression, which should be more than enough.
And as far as length goes I don't suppose that the factory is going to measure each one...

Bajaman · #15 03-25-2008, 10:17 AM

I took the tranny back out last week and took the original auto flywheel and the manual flywheel to the machine shop. The machinist said that they were both neutral??? So, I bolted just the auto flywheel on- no detectable vibration. Bolted the manual flywheel on- no vibration. Bolted the clutch and pressure-plate on- no vibration. Bolted the transmission on- Now I feel the vibration. Two possibilities present themselves. One the absence of the third mount transmitted less vibration to the body. The other possibility is that there is something in the tranny causing an imbalance. The second point does not seem very likely, as I feel the vibration with the tranny in gear, and the clutch disengaged in the driveway...
I replaced all the mounts (two engine and one transmission). I guess it's possible that the mounts are all a little stiff at this point.
Other thoughts?
bb