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Weeman83 · 12-12-2007, 10:07 AM

Hello guys,

How do you tell the difference between rear differential noise from wheel bearing noise? I know the usual trick is that wheel bearing noise will amplify or disappear depending on which direction you turn, and ring and pinion noise will change with throttle lift off.

My problem is, this noise only changes pitch with road speed, and nothing else! Throttle or not, turning not...it's the same, and just gets whinier with speed.

Anyone else had this problem? How do I pin point the noise?

Note: I just changed the diff fluid with Redline 75-90 and the noise did not subside.

Al Canuck · 12-12-2007, 10:18 AM

Possibly a driveshaft centre bearing?

Weeman83 · 12-12-2007, 12:16 PM

Hmmm, the sound is way too far back to be center bearing I thought.

redhatpat · 12-12-2007, 04:19 PM

If you have an open diff you can jack up one wheel at a time and run the drivetrain to listen to one side at a time.

Weeman83 · 12-12-2007, 04:31 PM

Originally Posted by redhatpat

If you have an open diff you can jack up one wheel at a time and run the drivetrain to listen to one side at a time.

best thing i've heard!!!!!

direction88 · 12-12-2007, 07:24 PM

Originally Posted by Weeman83

best thing i've heard!!!!!

WTF another "so called" is without a LSD?! With the 4 cyl 4.10 LSD so rare what is the solution for you one legged boys?! Could you run the 6 cyl/M3 rear end realistically?

Nick · 12-12-2007, 07:37 PM

What condition are your rear subframe bushings in? The diff. noise in my M3 became more pronounced when I swapped in stiffer subframe bushings.

Noises can be deceptive, it may help to have somebody sit in the back seat (or trunk

) with their ear to the floor while you are driving, to really pinpoint the sound.

Weeman83 · 12-13-2007, 12:16 AM

Originally Posted by direction88

WTF another "so called" is without a LSD?! With the 4 cyl 4.10 LSD so rare what is the solution for you one legged boys?! Could you run the 6 cyl/M3 rear end realistically?

There are 6cyl 4.10 LSDs that came on late 325is's I believe.

Al Canuck · 12-13-2007, 01:58 AM

Originally Posted by Weeman83

There are 6cyl 4.10 LSDs that came on late 325is's I believe.

Most of the M20 4.10's came in automagic 325is's. Interestingly enough, Mike's 318is has an open diff, but get this, it's a 4.27!

If you want, bring the car in on Saturday, and I should be able to pinpoint the noise on a test drive. If not, we can run it on the hoist while I nose around under it with a stethoscope.

Al

Weeman83 · 12-13-2007, 02:08 AM

Originally Posted by Al Canuck

Most of the M20 4.10's came in automagic 325is's. Interestingly enough, Mike's 318is has an open diff, but get this, it's a 4.27!

If you want, bring the car in on Saturday, and I should be able to pinpoint the noise on a test drive. If not, we can run it on the hoist while I nose around under it with a stethoscope.

Al

Darn, I am busy saturday. I'll call you when life gets less crazy. Thanks Al!

12-12-2007, 10:07 AM	#1 (permalink)
Weeman83 Senior Member Joined: Oct 2007 From: Richmond Posts: 1,293 iTrader: 0 Thanks: 13 14 Times in 9 Posts Weeman83's pictures '91 BMW 318IS	Rear end howl... Hello guys, How do you tell the difference between rear differential noise from wheel bearing noise? I know the usual trick is that wheel bearing noise will amplify or disappear depending on which direction you turn, and ring and pinion noise will change with throttle lift off. My problem is, this noise only changes pitch with road speed, and nothing else! Throttle or not, turning not...it's the same, and just gets whinier with speed. Anyone else had this problem? How do I pin point the noise? Note: I just changed the diff fluid with Redline 75-90 and the noise did not subside.

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12-12-2007, 10:18 AM	#2 (permalink)
Al Canuck Banned Name: Al Joined: Jul 2005 From: Surrey, BC Posts: 1,850 iTrader: 0 Thanks: 4 3 Times in 3 Posts	Possibly a driveshaft centre bearing?

12-12-2007, 12:16 PM	#3 (permalink)
Weeman83 Senior Member Joined: Oct 2007 From: Richmond Posts: 1,293 iTrader: 0 Thanks: 13 14 Times in 9 Posts Weeman83's pictures '91 BMW 318IS	Hmmm, the sound is way too far back to be center bearing I thought.

12-12-2007, 04:19 PM	#4 (permalink)
redhatpat Senior Member Joined: Feb 2006 From: Pitt Meadows Posts: 866 iTrader: 0 Thanks: 2 1 Time in 1 Post	If you have an open diff you can jack up one wheel at a time and run the drivetrain to listen to one side at a time.

12-12-2007, 07:37 PM	#7 (permalink)
Nick Senior Member Name: Nick Joined: Dec 2004 From: Vancouver Posts: 191 iTrader: 0 Thanks: 0 1 Time in 1 Post Nick's pictures	What condition are your rear subframe bushings in? The diff. noise in my M3 became more pronounced when I swapped in stiffer subframe bushings. Noises can be deceptive, it may help to have somebody sit in the back seat (or trunk ) with their ear to the floor while you are driving, to really pinpoint the sound.

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