Is this clunk in my differential - PeachParts Mercedes-Benz Forum

RML · #1 03-14-2008, 11:59 PM

I am driving an 84 300D and am trying to diagnose a sound I hear and feel in my drive train. I feel a bit of a rumble from the rear when I am slowing down and almost stopped. It kind of feels like gears changing with too much play. I got under the car and looked at the flex disks and they look almost new. I concluded that the PO changed them relatively recently. Also, when I am cruising along at a relatively low speed, say 25 mph, if I hit on and off the gas pedal, I can feel a most definite play in the drivetrain. Could this be gears in the differential that are worn out. My next inclination is to empty the diff and take off the cover to have a look. What should I be looking for?

Thanks for any input.

t walgamuth · #2 03-15-2008, 12:37 AM

Don't bother to remove the cover. Put it in neutral in a safe way so the you can get under it without danger and see how much play there is in the pinion gear....if its more than about 1/12 of a rotation you have a lot of wear.

The diffs almost never cause trouble. I would look at the half shafts for wear. The cv joints last a long time but they eventually wear out and need to be renewed.....could be anywhere from 100 thousand to three hundred thousand miles depending on usage.

Good luck

Tom W

turbobenz · #3 03-15-2008, 01:30 AM

the deep clunking sound when you slow down is probably because your transmission vacuum isn't adjusted right or you have a vacuum leak. If its the same clunk I know, thats what it is

pawoSD · #4 03-15-2008, 02:19 AM

Quote:

Originally Posted by turbobenz

the deep clunking sound when you slow down is probably because your transmission vacuum isn't adjusted right or you have a vacuum leak. If its the same clunk I know, thats what it is

Oddly, mine has done this for the past 62k (entire time I've had the car), even after a removal/reinstall of the tranny for new seals by the dealer. It shifts wonderfully when accelerating though, it just clunks at 17mph when slowing down. "oh well" Neither of our other two do it....but my dad's 300SD has lots of slop/wear on the diff, it will probably need replacement at some point.

hangit · #5 03-15-2008, 08:08 AM

Did you inspect the U-joint? Even though everyone says they almost never go bad, mine did. If that's your problem, you will have to replace the driveshaft.
http://www.peachparts.com/shopforum/showthread.php?t=208875&highlight=u-joint
John

pawoSD · #6 03-15-2008, 10:39 AM

Yes when I had my shaft out it did have some play/notches in the U-joint....it is probably the issue....but I have no vibration when driving, and don't want to pay for a new shaft either....

mobetta · #7 03-15-2008, 11:20 AM

I was getting some clunking in my car especially when changing directions-fwd-rvrse. I crawled under it, looking at everything. what I deduced was the halfshafts. the boots were still good, so I went and got my trusty turkey frying marinade injector horse needle.

about 2-3 good doses per boot, and a few days later, and ever since, it's been quiet.

yes, I am cheeeep.....

hangit · #8 03-15-2008, 02:13 PM

Quote:

Originally Posted by pawoSD

Yes when I had my shaft out it did have some play/notches in the U-joint....it is probably the issue....but I have no vibration when driving, and don't want to pay for a new shaft either....

Pay a little now or a whole lot later if it fails under speed. I'm not sure if a U-joint failure would end with the same results as a flex disc failure. Not pretty from pics I've seen on this forum or dieselgiant's site.

John

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