Further Update:
 

Well, it seems that WhiskeyDan wins the prize. My Indy says it's the U-Joint. I'm not really sure where this leaves me, though.

Is there anyway to rebuild a U-Joint? This is not something I want to attempt, I'm just curious if it's possible and who would do it.
A new driveshaft is over $1K. I plan on keeping this car for a while but if a used shaft will suffice I would rather go that route for financial reasons.
What driveshafts will fit in an 85' 300SD? Would a later model 126 be the best bet or should I try and find a good example of the same model and year? Is it even possible to find a good used driveshaft? This car only has 100K (at least as far as I know) so I'm skeptical about finding a good used one.

Hi,
My dad's W115 240D does this too jacked up both wheels off the road and when you put it in first and let it run on idle with the back wheels spinning this happens but as soon as you give it a little throttle it goes away, I'm pretty sure its not the CV's or the diff... I removed all that and was quite miserable to find there all ok so I had to put it back together and couldn't solve the problem, nothing is hitting scraping against or interfering in anyway with anything prop-shaft ect all moving fine with no signs or interference its kinda like almost a rumbling sound I also healed each wheel with a ratchet with the opposite one spinning to check if it was coming from that specific wheel but with each wheel healed in place and the opposite spinning the noise didn't stop...... It's hard to say if it was coming from the prop-shaft because I installed a different one and the noise continued......the huge clamping nut that clamps the small prop from the gear box to the larger one with the UV join is tightened well although the UV joint wasn't new I couldn't find any play in it...... I'll be removing the CV joints to install new boots so I could have a go at this problem too :rolleyes: ( and I guess I'll make a small video....I've got this easy method to install OEM CV boots with no stretching, boiling or cutting ect... no one wants to believe me or try it so I guess I'll just make a video and prove it works fine and is easy so ppl can use this method for proper OEM's!!!! ) :D

Jeremy

You or your mechanic won`t be able to replace the U-Joint on a MB. It had to be replaced at a driveline shop that has the set up to work on these.
The U-Joint is staked in, and not held in with the C clips like most U-Joints.

I just had mine replaced, cost $265. at South Bay Driveline in Jan Sose, Ca.

there is a shop in Portland, Or. and one in Texas that is mentioned here on the Forum. their price range is $400.
http://www.driveshafts.com/

http://driveshaftspecialist.com/Import%20html/Mercedes.html?gclid=CImkgrmfyqACFRNZbQodCEvJaw


Charlie

B Hutch I just posted a new thread on such diff, before I read your issue. I was NOT able to find a good second hand diff to replace my 85 SD which had ABS and installed one without the speed sensor connection. I have 301K miles on my car now and must have put about 50K on the changed-out one. I'm pretty sure you have a bearing issue, but I'm not so sure if there is a reliable shop that can do the work. If there is, I'd like to know too. Good luck...

As mentioned previously, my Indy thinks that it is the driveshaft and I will probably do a swap sometime in the next week or so to verify. I'm still not 100% convinced either way but a driveshaft swap will tell us a lot. As far as rebuilding goes, the only thing I know I've read on this forum and it appears to be a pretty involved task that required preloading the bearing and special tools. I'll keep you posted.

Even further update:
 

Well, a rebuilt driveshaft did not fix the problem. I got the rebuilt from Driveshaft Specialists out of San Antonio. They include new U-joint, new center bearing and carrier, new centering sleeves. No love. So, I'm leaning towards my original diagnoses.

I had a growling that sounded a lot like what you described: speed and load related but not turn related, and it was even at a tempo that agreed reasonably well with the rate of spin of the drive shaft. I too chased around the driveline thinking it was somewhere in that system. I lucked out and it started to get much worse fairly quickly. Turned out to be a front wheel bearing, which I managed to replace before the metal flakes caused it to sieze on me suddenly.

YMMV, but just because it looks and sounds like a duck, doesn't mean it isn't a hunter instead.

Poo hope it didnt cost too much. I have yet to hear of one actually going bad. They are not typical u joints in that they dont bend much at all. 2.88 rear ends are not that easy to find, when you need one.

The rebuilt driveshaft cost about $370. I paid my Indy $100 to put it in because I've been too busy. There is also a $60 core charge but I'm considering keeping the original shaft since it only had about 100K miles on it as some cheap insurance against the rebuilt, although it seems of high quality. All in all, an expensive dead-end. My Indy swore up and down that it was the driveshaft so that dosn't reflect that well on him. He does good work for fair rates but I'm begining to think his trouble-shooting skills aren't that good.

That's interesting about the front bearing being the culprit for the previous poster. I'm going to bring the car to another mechanic in town with a good reputation and see what he thinks. Other than differential or bearings I'm out of ideas.

well above in post# 33, i mentioned I replaced my U-Joint. mine had movement in the old one when moving the shaft. hold the front piece and the rear piece, and there was definately movement.

it was replaced with a grease able joint. It was sent to a machine shop that machined out the staked area or what ever they do, then a new one was pressed in with the "C" clips. they said to give it a shot of grease about every 10k.

Charlie

As Layback was saying earlier , I think your going to find its the pinion to ring gear clearance . If it sounds like mud tires and changes tunes when the pedal is pressed its backlash. My wife's new 300 SD does the same thing. My 2006 F650 has made that noise since brand new , so loud you cant even talk without pressing on the pedal. Ford told me it depends on how the gears are set up. Mine being on the loose side. Yours could be worn therefore giving the same results.

Try changing to a heavier lube and see if it quiets down. 85/140 with some Lucas oil additive. If it quiets down you have some wear.

Thanks for the tip on the drive-line place I live in San Antonio and didn't know they did these. :thumbsup2:

Good luck !

I think Driveshaft Specialists take their work pretty seriously. I should add that the price included shipping for the part and core return.

Also, I'm pretty sure I noticed that the noise was more pronounced after changing my gear oil to synthetic 75-90. I will definitely try a heavier gear oil and see what happens. I could be prepared to live with it for a while if there is no danger of sudden failure. Has anyone ever found someone that can rebuild these? Surely somebody has the proper set-up.

I just found this:

http://www.dippy.org/svcman/sm03.html#REARAXLENOISE


All you want or dont want to know about rear axle noise..........;)

Final Update(?)
 

Swapping out the differential appears to have cured the noise. Hopefully the replacement differential will give some miles.

In investigating the noisy differential that came out of the car, I think I might have found the source of the noise. I apologize in advance for not knowing the proper terminology for the parts inside.

The "ringed" gears that accept the splined part of the half-axles have at least 1/16" of play in their "races". In other words, if you reach with your hands into the holes on the side of differential and grab hold of these gears, you can wiggle them at least 1/16", side to side and up and down. I'm assuming this is not normal?

How possible is it to rebuild a differential? If those gears are not supposed to have play one would assume that bearings could be replaced if it is possible to disassemble. Probably not a DIY, but maybe some shops could do this?

BHutch,

I read your thread with a lot of interest as My W111 Coupe is doing exactly the same thing: a light rumble as soon as I ease on the gas pedal at highway speed. The noise disappears if I either step on it or release it completely.

What you describe is some play of the differential's side pinions in the carrier. In my view this would have yielded noise while turning as play in the diff pinions may become appearent when they rotate against eachother?