[tmandel]

A couple of weeks ago, my wagon had a *hard* shift on a cold morning. A pretty big "thunk" sound.

Immediately thereafter, and ever since, I've had a strange sound -- rather like a card in the wheel of a bicycle (but more muffled, less sharp).

The sound only occurs when I take my foot *off* the gas pedal.

I do know that I need a new front differential -- there is a tell-tale whine, and when I changed front differential oil there were many metal flecks in the old fluid. I didn't see this, btw -- but my mechanic is *extremely* trustworthy, thorough, and *not* a promoter of unnecessary work.

The hard shift and thunk occurred a couple of days after transmission flush and refill. This was done via a machine, btw -- the pan was not dropped. We flushed it twice in fact, in order to produce a completely new-looking fluid.

My mechanic thinks the problem is front propeller shaft, which we all know (and he does too) is unusual. Oddly, the shaft seems to be a rebuilt unit, rather than the original propeller shaft.

He removed the shaft, found that the "slip yoke" (if this is the right term) was dry, unlubed, and he lubricated it and put it back. The problem seemed better for a day or two, but it is back.

Thoughts?

 

[tmandel]

One more point -- the sound varies w/ the speed of the car. Not with the gear it's in or the engine rpm. And, only occurs when I release the gas pedal (as mentioned above).

 

[tmandel]

No help? No ideas?

 

[loubapache]

Well, it has only been a few hours since you posted the question and most members have real jobs to do.

Does this noise last more than a split of a second? If yes, then try to put the transmission in neutral when it does it.

Your noise could be from the transmission, the front differential or the universal joint between the propeller shaft and the front differential. From your description, your mechanic greased the connection between the propeller shaft and the U joint. So that is one possible place for this noise. This takes a Molykote grease (long-term grease).

Also the instruction cautioned to pay attention for installation position of the rubber sleeve onto propeller shaft with universal joint and make sure it is properly seated.

 

[tmandel]

Lou -- yes, of course; sorry not to have been a bit more patient. :surrender:

The noise is continuous; it starts when I take my foot off the gas pedal at any speed, and it continues until I put my foot back on the gas or the car comes to a stop. The speed of the noise (again -- think of a card snapping in the spokes of a bicycle wheel) varies with the speed of the car.

The noise continues if I shift into Neutral. The transmission makes its shifts perfectly. For that reason, I am hoping it's not a tranny problem (and because a tranny problem sounds *expensive*.

As the connection between propeller shaft and u-joint was found *dry* perhaps there is wear and play that is causing this noise. I'm going to take the car to him tomorrow, and I hope we'll know more. It's hard to test for the noise itself while the car is on the lift, however.

 

[loubapache]

You can take this information to him so he can recall if he did according to this.

However, my gut feeling is that the noise is not related to any of the drive train components, simply from the fact you continue to have the noise when the transmission is in neutral.

 

[tmandel]

Hmmm, that's kind of a good point! :thumbsup:

I need to confirm what I said about what happens when I shift into Neutral. Will report back tomorrow.

 

[mbvis]

"The hard shift and thunk occurred a couple of days after transmission flush and refill. This was done via a machine, btw -- the pan was not dropped. We flushed it twice in fact, in order to produce a completely new-looking fluid."

Automatic gears use the principle of fluid mechanics.
I think the noise that you hear (card hitting the spokes of a bicycle wheel) is the "transmission fluid flung to the blades of the turnbine"
How did you flush the transmission twice with a machine when the normal procedure is to drain with taking the pan off? Was some chemical detergent used then got vacuumed out?
It could be the fluid type is wrong or the detergent residue was mixed with trans fluid or too much or too little fluid put in.
HowStuffWorks "Torque Converter Parts"

 

[Musikmann]

mbvis has a valid point. If the noise began after your transmission flush it stands to reason that is at least partly to blame. I'm pretty sure that's the way my dealer does a flush too (leaves pan intact) and although recommended by my favorite tech there, I'm not convinced that's the way to go. But since you have a 1999 with a torque converter drain plug, why didn't you do the more conservative drain/fill most often recommended by the experts here? I hope it's not a transmission issue, so good luck with that.

 

[tmandel]

Musikmann -- after lubing the U joint/propeller shaft about 10 days ago, the noise seemed to go away. It has since returned. The transmission shifts *perfectly.*

It may all the same have something to do with the tranny. Hope to find out soon.

As I mentioned, the transmission was flushed twice. The 2d flush included no detergent, so I don't think there's any in there. We used MB approved fluid of course.

I'll report back, and if the machine flush did cause a problem, then at least my pain will have the benefit of providing a good reason not to do transmission service in that way.

 

[Musikmann]

tmandel, I temporarily forgot about the U-joint/propeller shaft lubrication job. I was focused on the mbvis post which at the time made sense. Like you, I doubt there's any detergent remaining. In any event, good luck with your issue and please report back.

 

[tmandel]

Maybe it's *not* in the drive train...?

...my gut feeling is that the noise is not related to any of the drive train components, simply from the fact you continue to have the noise when the transmission is in neutral.

And I've confirmed that fact -- the noise does not change in any way when I shift into Neutral.

Dumb question: Does the propeller shaft continue to turn when the car is moving but the tranny is in Neutral?

 

[mbvis]

tmandel, I temporarily forgot about the U-joint/propeller shaft lubrication job. I was focused on the mbvis post which at the time made sense. Like you, I doubt there's any detergent remaining. In any event, good luck with your issue and please report back.

There was detergent used in the flush? Was it safe for transmission. I hope that the chemical did not hurt any plastic or rubber part if there's any inside the transmission.

I'm only speculating based on the quality of the noise (card hitting spokes of bicycle wheel).
"The noise occurs when the gas pedal is released"
HowStuffWorks "The Stator"
That's when the fluid returns from the turbine to the centrifugal pump while striking the blades of the stator. If the viscosity of the fluid is not right, the flowing speed of the fluid will not be to specs, I think you hear the noise as the thinner fluid flinging the blades. The transmission still works but in the long run, who knows what will happen?
If it's my car, the possible fix for the problem is draining, removing pan, drain from torque converter then adding new fluid. 9 quarts x $15 = $135 is much cheaper than $5000 transmission overhaul. I'd save the older fluid just in case.

 

[tmandel]

mbvis -- Thanks for your attention to this. You are right; you are speculating. What you imagine may be happening -- anything is possible. But there's nothing to indicate it. The correct fluid was used, and there's no detergent in the transmission.

Please note that the noise remains constant when the transmission is shifted into Neutral.

Btw -- take a minute and fill out your User CP, so we can know where you are, what you drive, and so forth!

 

[tmandel]

My mechanic says the problem is definitely the front propeller shaft, which he says consists of two pieces that are splined together. There is wear in the splined fit (i.e. where the two parts join -- how to say this!!?).

I am having a very difficult time finding a front propeller shaft -- I'd prefer a good, used one or a rebuilt one. I've tried several sources. I'd prefer *not* to buy a new one from the dealer.

As I can't get on the electronic parts catalogue (I use a Mac), I can't find the part number, and I worry that I'm mis-describing what I need when I call, e.g. Potomac German (I've called several sources).

Loubapache -- you were kind enough to provide a drawing of the connection between driveshaft and front U joint. Can I ask you to provide me a part number (and the same kind of drawing if available) of the propeller shaft itself? If you can take the time, when you have it, I would be grateful.

 

[loubapache]

Loubapache -- you were kind enough to provide a drawing of the connection between driveshaft and front U joint. Can I ask you to provide me a part number (and the same kind of drawing if available) of the propeller shaft itself? If you can take the time, when you have it, I would be grateful.

Good Lord, MB does not sell the U-joint as a separate part. :crybaby2:

prop shaft: item 101: 2104104806
boot: item 104: 2024110297

 

[tmandel]

Lou -- thanks! Is your Russian good enough to navigate detali.ru? I'm impressed.

 

[loubapache]

Lou -- thanks! Is your Russian good enough to navigate detali.ru? I'm impressed.

You do not need to know Russian. Just go through the link in the sticky and English will be fine.

 

[tmandel]

Huh. I do find a link in http://www.benzworld.org/forums/w210-e-class/1368901-help-tips-diys-general-info-climate.html, but the links don't work.

Otherwise, I've looked and can't seem to find a link to the site of your image. Will keep looking, but if you pass this way again, please put in the link.

 

[loubapache]

Russian EPC

You then navigate to your car (210.282), then to Prop shaft, . . .