Weird clunking in rear W124 w/ASD
 

This clunking matches the speed of the car. Its louder on initial acceleration but remains, speeds up and gets softer as the car picks up speed. Its starts to happen whenever I have been driving for a little while and make a sharp right turn.

Here is the kicker, if I take it on the highway past 50mph it will cease and I won't here it again until I make a sharp right much later on in the week. Had the car up and took a look around to see if I could find anything loose and found nothing. Does this sound like a bad bearing to anyone? Or am I looking at a probable bad shaft?

I am going to see if I can get it clunking again this weekend then I'm going to drive straight to my mech. under 50mph LOL:D

ASD is the locking rear differential, right? If this is the case, then the problem may be the differential isn't quite unlocking. This will be unoticeable when the car is going relatively straight, but upon making a sharp turn, the outer wheel must travel further than the inner wheel. If the diff is locked, or partially locked, it means that both wheels must turn at the same speed. Obviously, this will complicate turning, and so if the diff is only a little locked it may make the grinding noise, and it may go away at speed because either the force of the speed causes the diff to unlock or the electronics behind ASD cause it to shut down at speeds greater than 50mph. Just a thought...

Ok my wallet just burst into tears:( I hope (pray) you're wrong. By the way there is no grinding, just a distinct clunk that speeds up the faster I go. With the windows down in sounds like metallic finger snapping.

Yeah, a metallic sound like snapping sounds like a partially locked pinion gear. However, I may be completely wrong! Don't give up yet. See if there is a fuse to the ASR / ASD System. Take it out and go for a drive. By the way, is the ASD light on in the dash? If it is not, this means there is less likely a problem with the locking diff. Good luck!

Rear end noise
 

Similar to my problem last Fall. Left rear hub carrier bearing. Drove me nuts and cost $$$ before I found a way to isolate it. Bought a car cell phone holder/amp that plugs into the lighter and extended the mic so I could put it on the hub carrier. I could hear the bad one while driving through earphones. Cell phone holders cost about $20 and that will be the cheapest item you will buy for this repair job. Good luck, Craig

PS - I have a have non ASD differential that I bought because I thought that was the problem but it was not. 3.06 gear ratio. 90K miles. $300 plus shipping if you need it. Can out of my 92 300CE. Craig

Differential?
 

O.K., what is for sale? The ASD Differential or the one with the 3+ gear ratio? My E320 wag has the final drive ratio in the mid 2's, and might be interested in a diff with a ratio in the3's. If this is whats for sale, what does that kind of ratio do the gas mileage and top end? Mine is an E320 turing wagon which was purchased in England and imported--all euro inside & out, no gov on the M104 twin-cam engine--can run 147 flat out (fac-spec) and although would never do this is nice, but would like snappier starts around town even at high end-sacrifice.

I was actually offering it to yal so we should give him first option. Its a standard NON ASD 124 differential. However, there were 2 different inner half shaft flanges used on these differentials. I would need to know the diameter of your inner flange to see if it would fit and you should consult an MB specialist to see if there are any other issues. The 3.06 ratio would definately give your TE better acceleration. But again, lets give yal 1st option. Craig

Trover Ok the ASD light has not come on yet:( If there was a partial lock problem wouldn't the light come on? Also wouldn't I hear the same clunking regardless of turn direction? I'll check the fuse to make sure I am not getting false info.

A bearing or carrier bearing was my initial thought also. There are no leaks and the shafts look very good. When I had the car up I took the time to do a diff fluid change just for the heck of it, I was hoping it would somehow help the noise. It didn't, it came back a few days later.

Craig you are right there is nothing more annoying than a sound like this that comes and goes. But when you hear this it feels like you are going to see one of your rear tires fly past you when you stop:) When something goes wrong in the rear of a W124 it echos through the interior. Is the bearing you are talking about at the wheel or towards the diff. Is it just a regular wheel bearing?

Thanks for the offer on the diff Craig, appreciate it, but I'd like to stick with the ASD if I can. It rocks in winter. But until I isolate this thing I have no clue how to proceed.

Rear noise
 

Yal - mine started with a high pinging noise that turned into a rumble between 25 and 45 MPH. However, when the rear wheels were off the ground, the bearings (at the wheel in the hub) seemed to be OK. This was also true with the engine running and letting the wheels spin - there was still no noise. As I mentioned before, there is no better way to isolate it than to put a mic back there in various locations and drive it, listening to the noises amplified in a head set. When I finally found the bad bearing the race was burnt and scored only slightly but it made a hell of a noise. No matter what, don't start throwing parts at it. My experience cost me nearly $2000 before I was all done just to replace a $70 bearing. Craig

Ok thanks. I'll do some more investigating. I'll report back what I find.

I've learnt from this forum not to throw parts at anything on these cars, you'll get into a hole pretty quickly.

If anyone reading thinks of something..chime in!:D

Hey guys my mechanic thinks that the clunking may be the parking brake so the car is going up this weekend.
ASD light finally came on. How do you read the fault code? Could I do it myself?

Found the codes...once again Mercedesshop is a mercedes encyclopedia...unreal:D


1: No fault in system
2: ASD control module (N30/2)
3: Stop Lamp Switch (S9/1)
4: Left Front Axial Vehicle speed sensor (L6/1)
5: Right Front Axial Vehicle speed sensor (L6/2)
6: Rear Axial speed sensor (L6)
7: No speed signal from Any sensor (L6,L6/1,L6/2), missing ground
8: ASD valve(Y38) or Stop Lamp Switch (S9/1)


The pin to read is #5, so now I have to make a makeshift reader. If anyone knows how to do this give me a shout otherwise i'll wing it.