[T4Turtle]

Hello, I have a 1999 E320 4MATIC with a strange fluttering noise. Sounds like something flapping in the wind. It has just turned 179K miles. The wiper cowl screens were pretty well shot, removed them to be sure this was the issue, still making this sound. I replaced the radiator a couple weeks ago and some rubber where the intake air flows to and blocks airflow to direct to radiator was torn, duct taped it up and still making this sound. Had the underbelly pan removed from a previous job and did not have it on so there was the wheel well rubber pieces hanging out in the wind so I remounted this and it is still making this noise. Front drive shaft feels tight, banged on all the heat shields and they are solid. Drives and shifts normal but feel like something is going to let loose at around 60 mph.

It does not make any noise revving it in park or with foot on brake under a load. Also if I start from wide open throttle to 60 mph no noise until I let off the gas.

I made a short video:

Motor mounts were replaced about 4 years ago. Transmission mount was not replaced.

 

[T4Turtle]

Thinking it has to be the front driveshaft flex discs. This video is better:

 

[mrboca]

Well, go under ancd check it out for cracks. Check the transmission mount too. Sounds like some shield is touching the flex disk.

 

[T4Turtle]

Cannot see anything wrong, shaft feels tight and hard to see the flex disc but not blown out looking like some I have seen. Just going to pull the shaft for a better look.

 

[T4Turtle]

Does the front drive shaft even have flex discs?

 

[T4Turtle]

Does the front drive shaft even have flex discs?

Appears they do not.

Front flex disc definitely has cracks so changing this anyway.
20220623_071717.jpg

20220623_102552.jpg

drive.google.com

Sounds like it is or in the front area like below the dash but I am sure these vibrations can travel, especially with an original transmission mount so changing this as well. The drive shaft feels solid.

 

[mrboca]

The flex disc / trans mount issues are generally associated with vibration in addition to some possible noise. Does the car vibrate at 40 to 60 mph?

 

[T4Turtle]

Appears they do not.

Front flex disc definitely has cracks so changing this anyway.
20220623_071717.jpg

Sounds like it is or in the front area like below the dash but I am sure these vibrations can travel, especially with an original transmission mount so changing this as well. The drive shaft feels solid.

The flex disc / trans mount issues are generally associated with vibration in addition to some possible noise. Does the car vibrate at 40 to 60 mph?

Some vibration but not real bad. The noise starts around 30 and I have not taken much past 60 as it sounds like something is going to let go.

 

[T4Turtle]

Having a hard time finding a transmission mount for 4MATIC, RWD is all I can find. They look the same, I can get one from Napa that states exact fit even if adding as 4MATIC. Napa Part #: BK 6201625

 

[T4Turtle]

Having a hard time finding a transmission mount for 4MATIC, RWD is all I can find. They look the same, I can get one from Napa that states exact fit even if adding as 4MATIC. Napa Part #: BK 6201625

Only place I could find it was here: 4MATIC Trans Mount

 

[T4Turtle]

Changed front flex disc and the old did not look that bad. This did not fix this noise. Changed transmission mount, also old one did not look bad and no real slop in it. This also did not fix this noise. Cannot find anything loose that would cause this.