Final Drive noise!
 

Presently, I have searched the entire technical forum in hopes of gaining some insight regarding my car's problem without alot of success. My 93' 325IS is making a metallic, scraping, repetitive sound that increases in volume as the car increases or decreases in speed. The sound is present, but greatly reduced when the clutch is engaged. Needless to say I have not been driving it and it is up in stands in my garage. I have checked the bearings for play, none. Diff fluid is clean and full. Before I put the car up I drove in sweeping circles in order to determine if the sound would subside as the weight shifted from side to side, it didn't. I am at a loss. Any insight someone could offer would be extremely helpful.

Check your brake pads and rotors carefully.

Brake pads and rotors you say? I'll do that then. Thanks for the reply.

You might also check to see how many clicks it takes to engage your parking brake. Should be about 3. If it takes less, perhaps it's too tight and the parking brake shoes inside the rear rotor are rubbing. OR maybe they're worn down real far and are scraping metal-to-metal inside the rotor. Not real sure about this but it's a possibility.

Those all seem to be likely possibilities. I appreciate the input. I'll definitely chech the parking break shoe, because I am at 140K and I don't think they have ever been looked at. Honestly, I am a little afraid that it is an internal problem within the differential, but its always better to check the other components first to rule out possibilities. Thanks.

I had this problem it was my rear breaks were bad, then a heat shield came loose., fixed that it didnt stop but got better , then it turned out to be my flex disk, when that got really bad though when I would hit hard in a gear it would make a thump thump thump until I changed gears. Otherwise the problems have been fixed, but those are the ones that was where my sound like that was coming from.

Thanks for the reply. I replaced my flex disk a little over a year ago and I have checked it since then and it appears fine so I don't think that is it. I have inspected my brakes quite extensively and no problems are apparent. At this point I feel it is probably the rear bearings. Not sure though.

Have you checked the CV joints? Because my car being rear wheel drive on the E36 I dont think I have rear bearings. I am not sure about that, but have you checked your cv joints?

Or your universal.

Universal is fine. CV joint(s) is another story. Thats a good tip, I had better check them. Last time I looked at them there was a fair amount of dried grease/oil on them and I cleaned it off...better check them again,eh? Honestly, this sound is so intrusive and loud at times I just figure it has to be something major like a bearing or diff. Also, I am pretty sure there are bearing in each side of the diff and in each outer hub, could be mistaken though. Thanks for the reply.

Have someone stand outside the car and listen carefully while you drive nearby. See which end of the car the noise is coming from.

noise in rear end.
 

I know what you mean we ruled out our cv joints. Thank heavens however I do know it going to come time soon since they are the original. But the noise it got really bad when it had something to echo off of, like a street that has houses close together it sounded horrible. With BMW I have found its a guessing game with these cars. And once you pin point the problem its trying to figure out what its called. LOL. Oh well they are so worth it though,

I appreciate all the replies. Very helpful information. Never considered driving by someone to see if they could pinpoint the sound. I will try that. And yes, I agree. They are definitely worth it. Where I live, people seem to respect the car, but tend not to understand when I profess my undying love of these cars. Could be because there are so few around here. I'd offer to let them drive it around so they could see what I am talking about, but I just can't bear to see her drive away from me!

This is what i did when i started hearing funny noises from my E36, I installed (4) 12" subwoofers and a 1000watt amp now my car sounds great! :) okay, how about this... How's your clutch? i had a clutch friction plate come loose and would rap against the bell housing sometimes. is there any chance that the differential has a little side to side play and may be slightly unbalanced? and... possible may be rubbing the aluminum heat shield when applying gas or downshifting which causes the drivetrain to toque to either side making something only rub then and not when the car is off on a lift? hmmmmm

I already have a band pass enclosure with a 12" in it, but I also have a UUC motorwerks system U exhaust that is just too sweet not to listen to! Anywoo, The sound is definitely not coming from the transmission or anything mid-vehicle. At this point I am about 75% sure it is diff related. I have listened to the diff using a wooden stick (sounds stupid but it works) placed on my ear and it is making one hell of a racket. The sound is somewhat audible just while it is running in gear. I am going to do a search to see if there is any way I can remove the cover and inspect the gears inside without removing the diff from vehicle. Also there does not seem to be any play in the diff mounts. I checked that right after I read your response. Thank you for the reply if you have any more thought please respond.

I had the same thing happen to me, and it was the rear left wheel bearing. I'm not sure thats your problem, but it's something to look in to.

Do u know if the bearing that failed was in the differential case or in the outer hub. It is my undrstanding that there are bearing(s) in both. It is not really critical that u reply I was just curious. Honestly, at 141K I am planning to have them replaced as soon as I have a little $$. I figure that will eliminate the bearings as the source of the noise and the job needs to be done regardless. Anyway, thanks for the reply, Nick.

Mine was in the outer hub, but I'm not sure if thats where your problem was

U only have outer wheel bearings ~:) When these cars 1st came out & we did diff service we use to get a little bottle of stuff to add with the ATF to stop that exact noise-->check with dealer & see if they still have it->whens the last time you replaced the fluid

Thanks for the response, cowboy. I was planning on changing the fluid this sunday, but decided not to based on your response. I will have to look into that fluid. Can you tell me any more about it? I was just imaging myself explaining this to the parts guy at a dealership and him having no clue what I am talking about. Its so hard to find good help these days...