Slight humming coming from rear of 318is

[alB5]

Hey, I'm having a strange noise coming from the rear of the car that sounds like two pieces of metal coming in contact. It's very slight and audible at lower RPM's. It only happens when in gear driving normally. When at say 35 mph, and am in neutral there is no noise coming from the rear, but once i put it in any gear it will start making this noise. It's pretty noticeable but the car still pulls fine and diff appears to be functioning.

By the way, does my 318is have a Limited Slip Diff? It's a Jan 1991 build date if that matters.

[grantlacey11]

You'll have to look under the car to see if you have an LSD. On the tag on the back of the diff there will be an "S" before the numbers if its a LSD.

That sound might be your diff going.

[Simon S]

If LSD:
1) a light 'spin out' in a dusty/loose gravel area will leave two 'spin out' marks.
2) with rear jacked up - spinning one wheel will cause other wheel to spin in same direction.
3) see above.

[ivo316]

Diff going, either the bearings or the ring gear/pinion, check the price of them and the price of a junkyard diff, if you can get one cheap drive it until it goes (it could last years). If it is too expensive, take it out, remove it, replace all bearings and reassemble.

OH, please check if you have oil in there, maybe just that.;)