Drivetrain "bearing" whistle - PeachParts Mercedes-Benz Forum

jissparks · #1 02-25-2007, 08:41 AM

I have a 99 ML320 with 110K miles that has generally given good service. About 2 weeks ago it developed what I can best describe as an intermittent high-pitched whistling sound from the drivetrain. I've poked around a bit and cannot see anything obvious. It's hard to locate the noise exactly, and you cannot hear it as a pedestrian when the car passes. The noise starts only after the car warms up, it is definitely related to vehicle speed rather than engine speed, and is unaffected by applying the brakes. The noise starts at about 35MPH. Initially I made it go away my driving a bit in lowrange, but that now has no effect. It sounds like a bearing, but where?
Thoughts?

azinn · #2 02-25-2007, 09:24 AM

Quote:

Originally Posted by jissparks

I have a 99 ML320 with 110K miles that has generally given good service. About 2 weeks ago it developed what I can best describe as an intermittent high-pitched whistling sound from the drivetrain. I've poked around a bit and cannot see anything obvious. It's hard to locate the noise exactly, and you cannot hear it as a pedestrian when the car passes. The noise starts only after the car warms up, it is definitely related to vehicle speed rather than engine speed, and is unaffected by applying the brakes. The noise starts at about 35MPH. Initially I made it go away my driving a bit in lowrange, but that now has no effect. It sounds like a bearing, but where?
Thoughts?

Have you ever changed the transfer case fluid? I have read many threads about noise from the transfer case being done away with by changing the fluid in the transfer case. Sometimes changing it several times in short intervals is necessay. According to some MB Techs, the transfer case fluid should be changed around every 50 to 60,000 miles. My 2 cents.

jissparks · #3 02-25-2007, 09:36 AM

I haven't changed the fluid and it looks like I should....was just reading some of the older posts that indicated that MB may have "changed their minds" regarding this.
Are there recommendations for fluids other than Dexron ATF?

azinn · #4 02-25-2007, 10:25 AM

Quote:

Originally Posted by jissparks

I haven't changed the fluid and it looks like I should....was just reading some of the older posts that indicated that MB may have "changed their minds" regarding this.
Are there recommendations for fluids other than Dexron ATF?

If you do the transmission, it should be MB trans fluid only. I think the transfer case is Dextron III. The owners manual has all the details.

jissparks · #5 02-25-2007, 06:19 PM

Changed the transfer case fluid and the rear diff fluid. Both looked a little dirty, but OK. This had no effect on the noise. I guess the next step is to replace the transmission fluid as well. Still think the noise is coming from the center or rear of the car, but....
It sounds like a bearing noise, or possibly an hydraulic noise--a high pitched whine.
I saw an earlier post suggesting clogged transmission filters could also cause noise.
The car is definitely trying to tell me something, if I could only understand it!

ILUVMILS · #6 02-25-2007, 09:24 PM

It sounds like the driveshaft center-support bearing is worn. It's a pretty common problem on older ML's.

ajvot · #7 02-26-2007, 12:40 PM

I had the same issue with my 98 ML320 with about 110K. The center-support bearing did the trick.

jissparks · #8 02-26-2007, 07:22 PM

The driveshaft support bearing makes sense to me given where I think the noise is coming from. It looks OK, and I don't know how to conveniently check it out without removing it (considered trying to squirt oil at it), so I guess I'll go ahead and replace it.
Thanks for the help. It just snowed here in RI so it might be a few days until I get to it.

jissparks · #9 03-05-2007, 04:50 PM

Back from a trip and looked at the part I ordered for the first time today. What keeps the dirt out of the bearing after it's assembled. The interior bearing on the part I received does not look completely sealed. The plastic cover over the race appears loose.
Any observations/suggestions appreciated.

vlowe · #10 03-05-2007, 10:32 PM

We had the same noise last week on 98 ML320, 205,000 km. Took it to MB and mechanic said center support bearing was gone. They replaced it and noise is gone. I asked for the old part back and on inspection noticed that bearing section appeared to be leaking out rust so water eventually gets in and bearing fails. At this mileage, I consider it normal wear, especially on a bearing that cannot be greased.