Excessive road noise, help!

[LRG SOUP]

The 40mph+ bit still points to diff noise for me, unless a CV joint on a rear half shaft has gone bad.

I will check those parts as well. thanks for the input! Would replacing the fluid for the diff solve that issue if it is the diff or buying a new diff necessary? If that is the case I will go to my local junk yard and pull one off of a 318is if I find one.

[ELVA164]

Would replacing the fluid for the diff solve that issue if it is the diff or buying a new diff necessary?

The first thing you should do is check the condition of the CV boots on either side of the diff and check their movement through one rotation. Look for binds, rough spots, or looseness. If the joints look good, then I would drain the diff fluid and inspect it. If the fluid looks overly metallic and/or dark, or smells burnt, then there is an issue or excessive wear in the diff.

[LRG SOUP]

The first thing you should do is check the condition of the CV boots on either side of the diff and check their movement through one rotation. Look for binds, rough spots, or looseness. If the joints look good, then I would drain the diff fluid and inspect it. If the fluid looks overly metallic and/or dark, or smells burnt, then there is an issue or excessive wear in the diff.

Ahh, thanks for the info I shall try that this weekend. We'll see if it improves...

[LJ851]

The 40mph+ bit still points to diff noise for me, unless a CV joint on a rear half shaft has gone bad.

Shortly after i first bought my E30 the rear wheel bearings went out and the noise was a high speed one as the OP states.

7 years and 100k miles later its time to change them again. However this time the noise is mostly at low speed like 15-20 mph.

If you can do this safely, put the car up on jackstands and accelerate the wheels up to their noisy speed and use a broomstick or similar as a stethoscope at the various bearing areas. It will be obvious which one is the offender.

When the diff bearings go you usually can change the sound of the noise with on and off throttle.

My Crystal Ball says rear wheel bearings.

[LRG SOUP]

^^^ haha crystal ball, I shall check the wheel bearings as well. I called my shop and asked about my situation, they said to jack the car up and and hold the rear wheels with me facing the when face and shake in a tilting action to see if the bearings are out... But thanks! I am narrowing this issue down for once! Replacing the diff fluid this weekend and checking the wheel hubs. I'll update you guys on what goes down.

[dustyperez]

i have this same problem. im interested to see what you find out.

[LRG SOUP]

ok I found out what was causing majority of the road noise. It was the wheels bearings. I only changed one since I had limited time at my friend alpineM325's house. So it was the passenger rear wheel bearing that was causing all the ruckus. I followed the DIY using the Harbor Freight tools (which worked remarkably!), took me about 5 hours to do it since I am not very mechanically inclined haha! But it drastically reduced cabin noise. I still have to change out my LSD fluid and possibly trans fluid to hopefully reduce more noise. Thank you guys for your input as it greatly helped my diagnose my failing wheel bearing issue!