My 83 300SD has a very odd rattling noise I am hoping someone can help identify.
The car has 350,000 miles and runs very strong but recently a loud rattle / knocking noise at idle and up to 1500 rpm regardless of load has me puzzled.
I was able to identify where the noise was coming from by using a stethoscope with a rubber hose. It was the loudest when placed into the inspection hole between the engine and trans.
I took it to my local import repair shop and with the car in the air found a cracked flex plate and a torque converter bolt sheared off, never seen that before.
I was positive this was causing my noise since it was exactly where the noise was the loudest.
I had the flex plate and the bolt replaced.
Installed the flex and the torque converter with all new bolts and.......the noise is still there, just as loud.

Has anyone ever heard of the torque converter making a rattling noise?
It has been suggested that the torque converter has play either internally where the input shaft fits or in the front pump of the trans where the converter flanges engage the pump.
I have no drive-ability issues at all, the trans shifts as it has for the 7 years I have owned the car.
The fluid is clean and has a new filter.

It sounds like it could be the torque converter but it's hard to figure something like that out. You may need to take it to a good tranny shop and have them look at it. I've had torque converters out on Mercedes cars and they all sounded like they could have something loose in them but there was nothing wrong with them. I'm wondering if the guy torqued the torque converter bolts to the flywheel correctly. I had a car long time ago that had a knock when idling and would make a terrible sound after revving the engine. It turned out to be simply loose torque converter bolts.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

All bolts have been replaced and properly torqued. Also no apparent other damage was visible during R&R of flexplate.

Anyone have any ideas or ran into this before? I am stumped...of course that does not usually take much.

I hope they didn't replace the bolts with ones that are too long. They could bottom out and seem like they're torqued right yet still be loose.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

This is not a bolt issue. All new parts and bolts were purchased from the local dealer and properly installed.

Has anyone out there in this great forum ever had this happen to them or diagnosed this on one you may have worked on?

I think I have the same problem on my 300D N/A. I'm taking it to a local trans shop that does alot of vintage work in addition to newer cars. I'll let you know what they say.

Kevin

1978 300D
1979 240D

Yelllowbenz,
Thanks, I appreciate the help. BTW where in MO are you?

I live about an hour west of Columbia. Had planned to take the car in this afternoon but the snow changed my plans. Hope to take it in on Tuesday next week.

Kevin

1978 300D
1979 240D

The flex plate is what the torque converter is mounted to Kevin.

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Gone to the dark side

- Jeff

Thanks, I thought the flex plates were in the driveline aft of the transmission.

Kevin
1978 300D
1979 240D

I'm not sure what those are called, flex-disk?

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Gone to the dark side

- Jeff

I'm mixing terms here. I'm thinking of flex discs. Here is a great thread that nails my/our problem and yes it does sound like the flex plate is the culprit. Thanks again Babymog.

Flex Plate Torque Converter?

Kevin

1978 300D
1979 240D

This note is not going to help the cause. One summer day I had a simular rattle. Thought to myself great the flexplate possibly by location. It was quite audible.
Next day the noise was gone and never returned yet. Still wondering what the sequence of events really was. In my past experiences noises that strong do not just go away by themselves. I am not complaining just still cannot figure what is was that caused it that day.

I don't see how the flexplate could cause a screeching sound...
with the hood open, and someone revving the motor, what does it sound like? and where?
is the screech up front? or down under the car sounding when listened to under the hood.
new belts, not installed properly, or the wrong belts could still easily screech.
also a polished alternator pulley with new belts on could still screech...

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