OK, I have a 2004 C320 with 85,000 miles. Last week it sort of clunked while driving, almost like it shifted gears really hard. I didn't feel a slipping, just a clunk into gear under mild acceleration. It also had a sound like driving over rumble strips on the highway for a brief moment when decelerating (this is why I'm wondering about it being in the rear end since it sounded like it was back there). I didn't drive it for a week, then took it out again. It did it once once after being warm and nearly driving for an hour. Left it sit for the weekend and it didn't do it this morning on my way to work. I am thinking I need to at least change the transmission filter and pan fluid, but am wondering if I should do a full flush or not. I am thinking I will, but what does everyone think here. Anything else to consider? I hope it is just old fluid as I don't think the coolant leaking into the transmission fluid is an issue, am I wrong?

 

if it is not the coolant leaking and causing the damage then I can say with almost 100% certainty that your tranny fluid level is not correct. check your level with a dip stick, .... yes, your car does not come with one but you can get one from ebay for like $20 and I am pretty sure your level would be low.

So i would start with that first, check the level at the right temp with the car running and make necessary adjustments and go from there.

 

Thanks, I'll try this first and provide feedback

 

Ordered the dipstick tool, will be able to pick it up in a couple of days.

 

Change fluid & filter.

Also check

Rear transmission mounting.
Propshaft flex discs.
Propshaft centre bearing.
Rear side shafts for cracked CV joint boots leaking grease

 

Will do, thanks. Um, full flush or just the pan?

 

you arent alone, mine does this as well.
but my condition is very specific....
mine does it from 3rd to 4th gear under very light pedal pressure at around the 35 mph mark, kind of like in between coasting and and giving it a little gas. since it is specific i can usualy avoid this, unless i get behind someone in town at around 30 mph, and they cant decide if they want to do 25, or 35 mph. it never does it cold, only after about 5-10 miles of driving.
it clunks pretty hard sometimes, first time it happened i thought i got rear ended.
my fluid was recently flushed, with the filter change as well, at the MB dealer. it didnt solve my problem.

 

I'll pay more attention, but sounds exactly like my condition except mine takes hot temps outside and more like 30 minutes of warmup time.

 

Yup, once warm, after about 30 minutes of driving, it jerks and only sometimes creates the rumble strip noise between 25 mph and 35 mph. Not sure what gear it is in but it happens when coasting or under less than 25% throttle. Wasn't over 80 F today, so just once the drive train gets warm I guess.

 

Unless the car has had it's regular 39K miles changes then full flush or 2 back to back half changes. If this is not effective then have all adaptions reset with a Star.

This rumble strip problem is unusual. Make sure that the propshaft spline is properly greased.

 

yeah, the noise is weird. That is why I checked the rear cv joints initially, but they seem fine. I'll post after this weekend, when I get the time to flush the system.

 

OK, I've done more research and saw the TSB on the radiators before 09/03, my car was manufactured 10/03, I would assume the glycol to not be an issue, but I bring this up because the symptoms include a droning noise.

I priced all the parts I need for a flush with the dipstick tool around $250, the dealer's price to do it all for me is $375, so I don't think it is worth me doing it to save $125. The job is rated at 1.5 hours. I also think I have a $100 certificate at home for service work! Either way I've made my appointment for Monday morning.

 

Have the used fluid checked for glycol immediately. You should be out of the Valeo radiator problem but check what radiator you have fitted. See identification in splinter's thread in DIY stickies.

 

OK, I'll crawl under it this weekend before taking it in. How/what should I tell the dealership to do on Monday? I am out of warranty, but can I get them to check for glycol and what if they find it?

 

All Benz dealers should be able to do a Glycol test. If there is glycol in the fluid they must replace the Valeo radiator with a Behr unit & flush the transmission first then refill with new fluid and fit a new filter. Then you have to hope that the glycol has not damaged the clutch pack facings or it's a transmission rebuild.

Take this to the dealer with you. It is in the Wiki.

https://mbworld.org/wiki/index.php/F...f_radiator.pdf

 

I spent a significant amount of time on this issue last year, it was exact same condition that you guys are describing, it would happen between certain speeds and i would hear loud clunky noises from the rear...after having done everything and i mean to the point where the stupid MB tech telling me to replace the entire transmission, i came across a post by Glyn where he mentioned that a slight change in the tranny fluid levels have a huge impact on the transmission and the first thing i did i checked the level and believe me it was just a few cm lower than it should have been, i bought ATF 134 and topped it up, i cudnot believe how fast the problem disappeared. I then came to find out that my stupid connector was leaking, replaced it and its been good so far.

 

But as Glyn mentioned, have your fluid checked for Glycol contamination, i had mine too and it was negative and thats how i was able to positively rule it out.

 

Grrr, my SA called, confirmed it is Behr radiator, no glycol per the test results, fluid level was full (within range is what he said), and didn't do a flush. Said there is another tech bulletin (not a TSB) describing the symptoms pretty accurately. He said they needed to "update" the software then do a reset to the electronic transmission computer (disconnect the battery is my guess). I am on the hook for 2 hours of labor, which seems excessive, I figured an hour tops. SA said that if this didn't fix it a rebuild of the torque convertor is likely needed and why they didn't waste money on a flush this time. I am going to do the flush myself after getting it back, but this is crazy. Any thoughts on what to say when I pick it up this afternoon. All they did was have the tech drive it with the service manager, then check fluid level, glycol and look up information in the computer. Why does that cost me anything? Grrr

 

Picked it up, issue seems to be gone. Invoice says 1 hour to test drive and confirm problem. Did glycol test at another 1 hour labor. No newer trans module software, they reset adaptation and that was all. Charged 2 hours at 120/hr and 4.80 for materials. I'm upset at the amount they charged for essentially only doing a glycol test and a 5 minute procedure to "reset adaptation"!

 

If they reset all adaptions on the transmission with Star that it no 5 minute job. 1 hour labor is fair.

 

You may not think so but you actually got off pretty lucky. Don't look a gift horse in the mouth If I were you I would drop the radiator pan, replace filter, and fill. Wait a couple thousand miles and drain and refill again. Replace the 'plug' while you're at it, it's fairly inexpensive and they don't last forever.

 

Mark - Presume you mean the transmission pan!

 

Yes....brain fart!

 

Ok, 2 hours labor for glycol test, 4 mile test drive total and software adaptation reset is fair? I'm just checking as maybe my expectations or understandings are in correct.

I will be doing the fluid change myself soon.

 

I don't think that is unreasonable as dealers go.

Get the fluid & filter changed. In an ideal world one would change the fluid & then reset adaptions but don't worry. The transmission will slowly adapt itself to the new fluid.