Strange sound when speeding over 80 MPH
 

Hey guys,

I have a 96 E320 with the M104 engine and a 4 speed.
I have had a strange sound that is barely noticeable for a while and was hoping someone may have any ideas as to what it may be.

Here is the scenario. When I drive on the freeway at speeds at or over 80 MPH I hear a very faint sound. It almost sounds like a low frequency grumble. The thing is, when I lift off the gas it goes away. If I press on the gas the sound comes on again. I thought it was the tires so when I got a new set I listened and it's still there. There is no noticeable vibration but only sound.

I don't think it's the tires or balancing on them.
I replaced the transmission and front flex disc about a 4,000 miles ago and the sound was there before this too. Who knows maybe it was always there and I just didn't notice it.

Does anyone have any ideas?

Maybe it's your conscience telling you to slow down.

I rarely drive this fast. That may be the reason I didn't notice it earlier.
On a lonely stretch of highway where the next town is more than 50 miles away doing 80 is following the flow of traffic.

I am not suggesting you go out and replace your exhaust system, but I have the m104 engine also and my car does the same thing ... I always just assumed it was either something with the exhaust system or just the way the car is

Do you notice it at the same speed as me or other? Maybe it has more to do with tachometer speed. I think mine was around 3000 RPM.
If it is just the exhaust I'm not gonna worry about it but I'm more concerned about safety issues if any at all.

Does it sound like sirens? Do you notice any flashing lights in the rear view mirror? I've had that issue before, it's an expensive problem to fix.

yea i notice it at the same speed as you and i believe same rpms