Manual Transmission Noise & Vibration - PeachParts Mercedes-Benz Forum

#1 09-19-2002, 03:03 PM

The vibration/noise problem on my 83 240D manual transmission (142K miles) has finally been narrowed down to the transmission. This after my driveline was replaced last week! I'm a bit frosted about that!

I took it to a different mechanic yesterday (Medi's in Concord, CA), he road tested it with me then hoisted it up, had his employee run the trans to 17 and 27 mph (loudest points) while we were under the car. When I placed my hand on the transmission, it was vibrating like the dickens, most at the above speeds. How much vibration is normal in a transmission? When it was engaged and starting off you could hear a sort of a soft grind until the driveline was spinning.

The fluid was checked, he had to stick his whole finger in to get to the fluid so it was very low. Drained transmission, fluid looked very dark with a bad smell. No metal parts or shavings in the pan. Replaced the fluid with 1 qt. Mercedes differencial oil and 1 qt+ with castrol ATF fluid. It shifts MUCH easier through the gears but still has the buzz and vibration in the car. Mechanic said to get rid of the noise/vibration the trans would need to be replaced but the fluid change would keep me on the road awhile longer if the noise/vibration didn't bother me (it does).

Questions - Could the problems be caused not by the transmission but the clutch? Transmissions seem to be indestructible right? What would a new, rebuilt or used tranny cost and to put in? While the tranny is out should I have a complete clutch job done? Don't know what bearings, etc. need to be replaced in that job? Could any easy items in the tranny be fixed/replaced without replacing the tranny that would cure the ill?

Thanks, Tim

Jim Anderson · #2 09-19-2002, 04:24 PM

Try coasting (in neutral and clutch out) at those speeds. That will isolate some stuff.

#3 09-19-2002, 04:33 PM

Do I understand correctly? Did this start when the driveshaft work was done? If so I expect that the drive shaft was not matched up with the spline correctly losing its balance. This is showing up in the transmission.

BTW. These transmissions do not use differential gearlube. They use engine oil or ATF. My 240D still has the original manual transmission after 533000 miles. Several hundred thousand miles ago I put 10W30 Mobil One in and have used nothing else since. The gear oil will make it difficult to shift in the winter and cause it to get very hot in the summer. I highly recommend changing it.

It would be worth a try to pull down the driveshaft, mark the two sections at the spline joint in the front shaft, disconnect the spline, turn it 180 degrees and put it back together. If it is that bad out of balance it is probably a full 180 degrees off.

Any time the driveshaft is removed, it should be marked at both flex disks and the spline joint and put back together in its original orientation.

I can't imagine what could be causing this that's inside the transmission.

Best of luck,

#4 09-19-2002, 05:20 PM

Larry,

I have had the noise/vibration problem from day 1 of owning the car (since march). The driveline switch was done because the mechanic said that was the problem. Obviously it wasn't! While under the car yesterday, the driveline sure looks clean with red and green paint lines at both ends, new flex disks look nice also! I just didn't need them!

I go back to Medi tomorrow to change the oil and filter since he put a small bottle of red stuff in my oil to see if it would free up the oil rings so I don't smoke so much. He said the oil rings may be compressed and this would help. Who knows! When he put it in, the car wouldn't start, then when it did it ran like poo for a few minutes, now runs fine. I am thinking of having him change the tranny oil out and put either Mobil 1 syn or Redline MTF in.

Thanks, Tim

#5 09-20-2002, 01:15 AM

Jim, I tried coasting in neutral and then reving the engine. Not nearly the noise or vibration but the was a small amount. What does this lead to?

#6 09-20-2002, 07:43 AM

Are you sure that your motor and transmission mounts are okay? On the 123 car they are inexpensive and easy to change. I had a motor mount make me think the engine had a dead cylinder.

Good luck,

#7 09-20-2002, 09:54 AM

Yes I had all new motor mounts put in, and I checked this while the car was on the hoist. I wish it was that! I'm pretty sure the transmission has waaaay to much vibration in it. It felt like a vibrator buzzing away when we were testing it on hoist (while the car was in gear reved to 17 mph. Transmission mounts were new also.

Jim Anderson · #8 09-20-2002, 11:07 AM

In neutral the drive shaft and a small part of the transmission is active, most of the rest is not moving, and the rest is turning at the engine speed. Putting the clutch in (should have suggested that too) will stop that part too. I think your transmission is at fault.

If you do take it out, change the clutch.

A story with a happy ending:
My wifes old Datsun had its oil leak out cause the case bolts had loosened. I re-filled it and tightened the bolts but it had devoloped a "sound." Then a couple of years later it started making real expensive sounds. When I took the drain plug out chunks of metal came out

It turns out it was the soft metal of a bearing cage that came apart and got chewed up by the gears. All I had to do was floss the teeth

they didn't seem to mind the bearing cage, and replace the bearing, dealer part, for all of $15

#9 09-20-2002, 11:33 AM

I did push in the clutch, while gliding in neutral, resulting in NO buzz or vibration. After all my other trys at having the buzz/vibration fixed, I agree with you, something is bad in my transmission. If I replace the transmission I will have the clutch replaced also. What are all the parts that should/can be replaced when a new clutch is put in? What are all the bearings to replace - pilot, throw-out? If I'm going to have it done, then I'm going to have everything done.

Jim Anderson · #10 09-20-2002, 02:08 PM

If you're having someone else do it, they will know what to do.

Other things: the pressure plate may need attention (replacing/resurfacing) and the flywheel surface checked too. The clutch slave is another part you'll pass on the way in.