Ok my car has been making this odd noise ever since I got it. Seems to run ok though so I've never been too concerned about it. It does drive me crazy though. Its a mechanical humming, almost like some sort of robotic arm moving, buzzing whatever you want to call it, maybe even a low pitch vacume cleaner. I'm not quite sure where its coming from, sounds like engine though (duh). Heres what irkes me. It doesnt happen in Park or Neutral or reverse. It doesnt happen when Im on the gas. And it seems to stop sometimes when I break. It happens when im coasting with no gas and the car is in motion. Can't say if it happens at higher speeds cause its too loud to detect. If I'm coasting, and its buzzing, if I apply a VERY slight ammount of gas the humming gets softer and changes pitch. A bit more gas and it goes away. Any ideas? (Sorry for long post, trying to be thorough)

 

Sounds like the rearend humming, from what you described. Might be time to change the fluid, or even worse, a rebuild.

 

Is the volume/pitch dependent on *speed* or on rpms? If speed, then StngKlr is correct.....my old '82 Bonneville has a leaky differential, and eventually the differential started doing just what you described. At certain speeds it would be louder...started low/quiet, got louder and raised in pitch as I sped up, then higher pitched and quieter until it was gone. about 15mph faster, it'd start again, though not as bad. When the speedometer quit, that was the easiest way to know how fast I was going lol. Actually kept me from getting tickets

 

could be the alternator.

 

No its not speed dependent, its throttle dependent. If i'm going10mph without depressing pedel, it hums. If i'm going 30mph and not touching the gas, it hums. As soon as I push the gas at any speed, the hum stops. If its humming, and I push the gas down VERY lightly, the pitch changes. After I apply a reasonable amount of gas (enough to notice a change in acceleration) the hum stops completely.

 

Sounds like a vacuum leak somewhere...

 

How can I find out where and fix it?

 

Sounds more like not enough preload on the pinion bearing or pinion nut, to me.

 

huh?

 

First thing id do is with the car running pop the hood and listen around the enging. then give it some gas and see if you can hear where the noise is coming from, that will help enormously when trying to locate the problem. it may be really obvious when you try this. good luck.

 

um... mine made a buzzing sound since i got it too, i didnt know where it was coming from, but i found out later that it was my speedometer cable, so maybe thats what it is, you never said exactly where its coming from I DONT THINK, i may be wrong, you may have, but if its in front of you, it MAY be your speedometer cable? hope that helps

 

Yeah it seems to be in front of me, hard to tell. As for listening under the hood, As I explained I can't. Because it doesnt happen in park or netural, only when the car is MOVING with no throttle. Sounds fine when its parked, reversing, neutral, or stepping on the gas.

 

hmm... sounds so much like what happened to me, till i got my speedometer cable, hmm... but it could also be many things, im just sayin that it could be that, because that happened to me ,

 

How did you fix it? Just swap the old one with a new one?

 

well what i done was, took it to my uncle, and he went and got a cable from a junk yard, you cant just get any cable from any camaro tho, theres certain ones, for year spans, or something like that, i dont think you can swap an 82 and put in a 92 ect. i may be wrong on that tho