Mercedes-Benz Forum banner

Rear differential making grinding noise

11K views 11 replies 5 participants last post by  Noodles 
#1 ·
Hey guys, my 06 320CDI (250k miles) has a noise in the rear. I got on the road from Savannah Georgia yesterday headed home and all at once, I started hearing a roar/grind sort of noise coming from the rear. As I drive home 4 hours, the noise would come and go with no particular relationship to any behavior while driving. If I could keep the car at a steady state (not accelerating or decelerating) it seemed the best. About half way home, it started a whining/whistling noise when I would slow down for a stop. Jacked it up this morning and got both rear wheels up and let her run in drive. I can't increase the speed b/c the computer seems to be holding it back to idle while up in the air (anti slip maybe??)

Both axles and joints seem to be ok - can't find any play in them and there is nothing noticeable going on. After a while I start to hear the noise (although not that bad at idle speed). I can hold either rear wheel to make the opposite one spin and the noise seems to be the same. In essence, it appears to be coming from the differential. I put a steel rod up against it and I can hear the noise. From reading some forums on this site, I see that some are saying that I probably need to change bearings. I have NOT changed the lubricant - I didn't realize I should have. So, I suppose I'm looking for some validation that the issue is what I fear and the best course of action. I'm mostly a DIY kind of guy so I may take on whatever rebuild project myself although I don't have a lift unfortunately.

I appreciate advise from those who have experience on this issue. How to rebuild, rebuild kit, any special instructions, etc.

Thank you guys!!
 
See less See more
#2 ·
It does sound like a bearing issue with the diff.

Now as to which one you will have to find that out. These are not known for eating bearings. Seeing as you said the noise does not change I would guess it is the pinion input bearing, but that is a guess.
 
#6 ·
You could put it into dyno mode, but do not drive it on the road that way. Every safety feature like ABS, TC, ESP and BAS are turned off.

Searching youtube for W211 dyno mode will show you the steps.

Once bit of caution. Several years ago a member had very tough time taking the car out of dyno mode. He finally did, but I can't find the post or remember what he did to get it out of dyno mode.
 
#7 · (Edited)
Update - I replaced the gear oil today. It was definitely low the old oil looked pretty sad. I spent more time listening to the noise trying to isolate where it was coming from. It's hard to tell. As I stated before, no matter which wheel I allow to turn I can hear the noise + it seems more prominent when listening to the differential itself - particularly the front where the drive shaft enters. The thing that bothers me is that the noise doesn't behave in a way that I would expect. For instance, when you can hear a noise and see rotating equipment at the same time, you can typically associate the noise with some movement. In my case, the noise seems to have a life of its own. I realize that there are gears inside rotating at different speeds than what I can observe (driveshaft and axels) but it just seems separate.

I'm doing my best to determine what part to focus on - like the front pinion bearings, Axle bearing, drive shaft, etc so I don't tear into something that is not broken. A question I have is.... Am I gonna have to take the whole Differential out to fix/rebuild it or is it likely that it can be fixed in place?

Also, I haven't seen anyone make a suggestion of how to rebuild if I get to that place. I'm considering taking it to the MB dealer and paying a diagnostic fee to get confirmation.

Help appreciated!
 
#10 ·
If the lube was low and it had 250k on the clock it's been driven 4 hours that way chances are it's the pinion bearing. Had exactly the same thing happen to my 228 only the parts weren't accessible. Because it was out I replaced all the bearings (3). Most likely you will be removing the pumpkin so if that's the case you need to replace all the bearings and then check it for backlash. If you aren't up to the task pull the pumpkin and take it to a well versed indie to replace the bearings and set the backlash. Good luck.
 
#11 ·
Hey all - thanks to everyone who offered support. I thought I would update you on the conclusions. After wrestling with finding the right ratio for my car (2.65) I found a used differential in a salvage yard in Texas on ebay. It came UPS pretty quickly. My son and I did the rip and replace job today, can't say it was enjoyable but I've done much worse projects. Konigstiger sent me removal/replace instructions and found them partially useful; some things were not very clear.

1) I removed the two exhaust pipes and muffler assembly; this was actually a very easy task.
2) Removed all the bolts from the Flex coupling connecting the drive shaft to the Diff. Separating the drive shaft from the Diff took a bit of crowbarring to get it back far enough to drop down. My Flex joint seemed in fine shape, surprisingly.
3) Removed the to bolts from the front mount and the one in the rear; the rear one is a pain in the butt b/c there's not much room to insert that E18 Torx socket and ratchet between it and the spare tire compartment. I had to use channel locks to grab the socket and back it out after about half way.
4) The removal instructions said to remove the emergency break cables but I didn't find it necessary personally b/c we once we dropped the diff down several inches, I removed it from the front mount by removing the 4 mounting bolts. If you planned to drop the diff all the way down to the ground with the front mount, you would need to remove the brake cables since they run through the front mount.
5) The two axles will slide out of the Diff but you have to take one all the way out. I took the right side out which required me to disassemble the whole wheel hub on that side then pull the axle out. Getting the axle to pull away from the diff required help from ole-man crowbar - but not too much. You feel like your breaking something. After removing the right axle, we pulled the Diff away from the left side axle; again - using the crowbar to assist. So we didn't have to remove the who axle from the left side hub b/c we essentially pulled the Diff itself towards the other side.
6) After pulling the old Diff out, putting the new one in went much quicker. It's a two-man job if you are on your back like we were on jack stands. It's a fair amount of pulling, jacking, shaking, pushing to line up all the holes. And the wheel hub is always a pain getting all the arms and bolts inserted while trying to hold them in place with the crowbar.
7) While reinstalling the exhaust system, my son over-tightened a clamp and broke one but other than that, no big issues. The car seemed to run as quitly as it did before. I will have to get another clamp sometime.
8) Drained remaining gear oil and refilled it with new.
9) Took her up the road a little ways and she seems quite. Can't say 100% for sure yet but I feel the Diff was the problem.

Thanks again for those who reached out to help me :)
Mark
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top