Why do 300SDs sound like that?
 

I have driven two differnt 300SDs now, and a 300TD. I notice the 300SD has a kind of "electric motor" sound to it when you are inside the car... Hard to describe, but it is like a humming, which changes pitch with speed. Kind of like an electric remote-controlled car. My 300TD had nothing of the sort. What is this? Am I crazy?

Could it be that both 300SDs had a misaligned exhaust pipe that was slightly vibrating on the floor?

I have it too, only happens when accelerating, disappears when you let go of the gas... Sounds like something in the drive line

Mine too!

Kinda like a turbo noise but lower pitch and comes on with acceleration.

Not the turbo cause with the windows down i can hear the turbo whistle.

I am thinking it is the fan but not sure.

My 300d did not do it with the same fan though so i don't know.

Steve

well, at least I'm not crazy... I haven't had a chance to drive mine a lot since I got it (problem with the alternator), but I noticed it with another one I drove before as well. It is strange that even though the car is mechanically very similar to the other 300's, it sounds so different. One of you MB nerdz will know what the sound is, I am sure.

I agree that the 300SD's sound different, but they also have a double fire-wall for sound insulation, and the car is a different chassis so it will resonate sound differently. Our 300D reminds me of a British taxi the way it sounds inside...low...diesely...pretty quiet. The 300SD has more of an engine sound, but is quieter overall. I like them both though. :D

I always wondered about 300E's as well. My friend's 300E had a lot of whine when it would accelerate. It sounded like a supercharger at times. I dunno if it was just gear whine, or just his car or if all 300Es are like that or what. But those 300E's are so quick compared to the diesels!

Yeah my 300SEL sounds like that at full throttle.

my 116 300sd has a different sound then my 123 300d as well.

Its probably gear whine, a lot of cars do it.

My 300SD does it, my neighbors Saab does it, and the 599GTB that drove past me today while I worked on a boat did as well.

I think its because of the way the gears are cut, I know on race cars its quite noticable, like you need ear plugs.

Hmm comparing a 599 and a 300SD? Odd comparison wouldn't you say ;)

Well for the purpose of this example.:D

An F1 gear box has a lot in commen with the 722.XX, yeah...:D

I'd say the same thing... but I hear it backwards... My TD has the whine and the SD and 190 don't. The TD supposedly has a rebuilt tranny though.

Hmmm... now that I am up and driving this car again, I was reminded of this thread today when my wife asked me "what is that sound that sounds like a jet?" I couldn't remember what you all said about it, so I came back to look...

Well, this sound definitely is not just with acceleration. It corresponds to the speed the wheels are turning and it comes from the rear of the car. It is actually at any speed, getting higher in pitch the faster you go. Gear whine sounds like the closest thing to me... it is definitely not the exhaust rubbing on anything and it is not limited only to acceleration, but I definitely heard this in both the SD I own and another one I drove.

Really I don't know how to describe it other than that it sounds a lot like an electric motor. I think golf carts probably sound like this, but I don't think I have ridden in a golf cart since I was about 10.

straight cut gears are loud...