lots of noise in back of car when in gear - PeachParts Mercedes-Benz Forum

surveyguy · #1 11-20-2010, 02:38 AM

oh boy people, drove my 240D 123 tonight, and i started hearing a clunking noise. not quite like a u-joint though. I was just going to change my rear-diff tomorrow, i hope that's not it.

it almost sounds like my lug nuts are loose on one wheel, which i will check. the noise is deffinately in the rear. thing is, it only makes the noise while i'm driving. if i push in the clutch, i don't hear it. put the clutch out, and step on the pedal, and noise returns. clutch in and rev engine, no noise.

it's really bothersome, probably because i'm fearing the worse. tranny or rear end.

any suggestions of where to look, how to test?

i sure appreciate this

whunter · #2 11-20-2010, 03:10 AM

Some Possible Answers:

* Loose wheel bolts = stupid thief tried to steel a wheel or you have an enemy?
* Bad axle and/ or the 13 mm axle mounting bolt/sleeve/washer has come loose = the shaft is walking in/out of the hub, chewing the splines threatening to rip out of the hub.
* Bad wheel bearing = rotor hitting caliper.
* Broken rotor = the Disc surface breaks away from the park brake drum.
* Bad carrier bearing and/or boot.
* Bad differential.
* Broken/damaged trailing arm = wrong axle angle.
* Flex Disc installed wrong?

.

surveyguy · #3 11-20-2010, 09:48 AM

thanks for the possible problem list. i will get out there in a few minutes and check into these. The previous owner had the carrier bearing replaced, but i'm hoping it's something like that or the lugnuts (I have a hard time thinking it will be lugnuts or bearings because it doesn't make noise unless in gear), and not any of the more serious (expensive/time consuming) sutuations listed. Also, since it does get more frequent the faster i go, perhaps again it will be a carrier bearing.

i sure appreciate others' experiences, and i will update for what i find while the search for the things on the list whunter gave me.

Guy

Biodiesel300TD · #4 11-20-2010, 10:46 AM

Does it do it when your sitting still or only moving?

I had some pretty good noise coming from the trans in my 240 that ended up being the pilot bearing in the trans. It would make the noise only when the clutch was out, would disappear when I pushed the clutch in.

Also check you sway bar links. They can make all kinds of noise. Usually rattling over bumps though. But they are cheap to replace and easy to inspect. They connect the sway bar to the hub in the rear. They are usually white(yellow with age), and are S-shaped. If the boots on either end are torn or missing replace them.

You should drive it up to my place this weekend, and we'll check it out!

barry123400 · #5 11-20-2010, 12:03 PM

Have a quick look at your flex disks just to make sure one of them is not coming apart before driving much. Probably just a cv joint though.

surveyguy · #6 11-22-2010, 01:09 AM

i took the car to my fav. tire shop. they looked at it. the only place they could get noise/movement from was one of my rear axles. it is odd, i've never had a c/v joint car before, or at least never had a c/v joint go out. we could turn the axle by hand a little back and forth and hear the "clunking" slightly. it's sure odd to me, i only hear the noise when moving and in gear. the boots are cracked but not leaking (yet) so probably will order the axles and do them both.

sound reasonable to you people, that this is probably my issue?

also, i need rear shocks. is it going to be easier to do them with the axle out of the way? since they're in the coils, i'm just wondering if i need to compress the springs and move the swing-arm (trailing arm)???

thanks so much

Guy

Renntag · #7 11-22-2010, 01:20 AM

Without looking at the rear suspension, I cant comment on the shock replacement, but I can say that it is common to rebuild the axles rather than replace them.

As stated above, you mention clutch engaged and disengaged, and engine revving, but you never mention "vehicle in motion", "Vehicle NOT in motion". Those two testing conditions are important right now. Clutch engaged and disengaged while vehicle is in motion and not in motion are good tests for this sound. Also, does it make a difference if when the vehicle is in motion that you are on and off the throttle, positively and negatively loading the drivetrain. This might exaggerate an axle or drive shaft issue if one existed.

Best of luck.

whunter · #8 11-22-2010, 01:52 AM

Quote:

Originally Posted by surveyguy

i took the car to my fav. tire shop. they looked at it. the only place they could get noise/movement from was one of my rear axles. it is odd, i've never had a c/v joint car before, or at least never had a c/v joint go out. we could turn the axle by hand a little back and forth and hear the "clunking" slightly. it's sure odd to me, i only hear the noise when moving and in gear. the boots are cracked but not leaking (yet) so probably will order the axles and do them both.

sound reasonable to you people, that this is probably my issue?

also, i need rear shocks. is it going to be easier to do them with the axle out of the way? since they're in the coils, i'm just wondering if i need to compress the springs and move the swing-arm (trailing arm)???

thanks so much

Guy

Yes the bad axle is a reasonable cause of the noise.

The shock procedure is the same for the W123 & W126.
Steps needed are:
#1. - #6.
#18. - 19.
Reverse this procedure to install..

Replacing the Rear Shocks & Springs on the W126 1985 300SD
http://www.peachparts.com/Wikka/W126RearShocksSprings

.

barry123400 · #9 11-22-2010, 02:09 AM

Quote:

Originally Posted by Renntag

Without looking at the rear suspension, I cant comment on the shock replacement, but I can say that it is common to rebuild the axles rather than replace them.

As stated above, you mention clutch engaged and disengaged, and engine revving, but you never mention "vehicle in motion", "Vehicle NOT in motion". Those two testing conditions are important right now. Clutch engaged and disengaged while vehicle is in motion and not in motion are good tests for this sound. Also, does it make a difference if when the vehicle is in motion that you are on and off the throttle, positively and negatively loading the drivetrain. This might exaggerate an axle or drive shaft issue if one existed.

Best of luck.

Too late to relube them when the noise is constant. If instead you drive say 100 miles and they start to get noisy then relubrication is a good possibility.

I would only change the one axle out but might refresh the lubricant in the otherside. A used axel from a wrecking yard is a reasonable risk after a relube expecially. . Just take the one from the opposite side of the donar car than your worn side. It costs no more and gives you a newer wear area. This is a better option than a chinese axle at this time I believe.

vstech · #10 11-22-2010, 08:55 AM

or one of mine rebooted of course!

surveyguy · #11 11-22-2010, 08:58 AM

thanks again for all the advice, to clarify renntag, i thought i mentioned this in my original post "while i'm driving. if i push in the clutch, i don't hear it. put the clutch out, and step on the pedal, and noise returns".:

to comment on Barry's post, that is the situation, it only seems to happen after warming up the differential. I was unaware these could be re-lubed. is there some zerk fitting i didn't see?

Also what you mentioned, is that i could rebuild these, i was unaware of this as well, sure sounds like it could be way less expensive. would i then order "C/V joint" or something like that?

i sure appreciate all the help, and i hope my re-clarification helped.

Guy

vstech · #12 11-22-2010, 09:02 AM

Quote:

Originally Posted by surveyguy

thanks again for all the advice, to clarify renntag, i thought i mentioned this in my original post "while i'm driving. if i push in the clutch, i don't hear it. put the clutch out, and step on the pedal, and noise returns".:

to comment on Barry's post, that is the situation, it only seems to happen after warming up the differential. I was unaware these could be re-lubed. is there some zerk fitting i didn't see?

Also what you mentioned, is that i could rebuild these, i was unaware of this as well, sure sounds like it could be way less expensive. would i then order "C/V joint" or something like that?

i sure appreciate all the help, and i hope my re-clarification helped.

Guy

it's not a good idea to rebuild the axle that is making noise. the other one is a good candidate for relube and oil.
you COULD pull the axle and mark it well, then reboot and relube then reverse it's side, and pray the damage done is not too severe. but I'd not chance the labor and expense of the boots and oil on a clunking axle.
if it's making noise, there is wear, likely the oil has seeped out of one of those cracks, and metal fatigue has worn the spiders. I'd replace with a rebooted axle from a salvage yard, or get one of mine if you haven't the space to do your own axles.

surveyguy · #13 11-22-2010, 09:16 AM

thanks for all the information John, i do see re-boot kits, there is outer/inner/annular/homokentic (the homokenetic looks like the right one in the picture, has a drum, but on the parts store picture they say "outside".

vstech · #14 11-22-2010, 09:39 AM

I use astoria Flexx boots, they install with a special pnumatic gun that stretches the boot over the can. the other style requires you to disassemble the boot, and some require removal of the can itself and it needs to be crimped back on with a special press. if you want to put your own flexx boots on, the astoria gun should be in the tool rental program.