w203 2002 722.6 transmission issues

Oct 22, 2014 | 07:41 AM

MBenzW203

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Mercedes-Benz W203 2002

w203 2002 722.6 transmission issues

Hi all !

First things first, I'm a random guy who knows pretty nothing about anything on my car. I have been looking at threads out there for quite a moment now. And I haven't found a solution to my issue yet. So before throw stacks to my dealer I decided to write down here my exact problem.

I have a 2002 w203 C-Class 180K. I bought her with 137'000km now she has 143'000km. I live in Switzerland and have the chance to speak a little english. Please excuse my writing or syntaxe may be faulty.

Some of you might find this thread similar to many other. It is sightly different actually. I have done quite a bit of research and nobody has my exact symptoms for this exact model. Sofar I havn't managed to deal with my issues

Moving on !

First I want to mention that I have no codes showing up at the moment.
I don't have a Star but I do have a OBD II Code Reader.

Since I bought this car the 722.6 5G Tiptronic transmission seems to have something wrong with it.. My symtomes :

When smooth cruising only like really gentle on the gas, 2->3 shift engages pretty brutally compared to the others. I mean like if the car was pushed from behind, it feels like it's shuved in to gear there is nothing smothening the operation like for the other shifts. Other than that 1->2, 3->4 and 4->5 seem to shift perfectly.

I noticed that whenever I floor the pedal I do not feel this symptome at all. Actually the more I press the gas the smother the shift. The gearbox seems to get the right information for shifting with more gas

Now I've noticed that the downshift from 3->2 is kind of similar in a way it is also brutal. Other downshifts are ok.

I've read somewhere that could be due to the Pressure Regulator Spring Valve in the valve body but that's on models till '99 so **** me right?

Beside this, I have another problem and I don't know if it has something to do with the first or what. The gearbox seems to "slip" or "lag" (I don't know what word to use) at some times.

For example: when I accelerate the gearbox gives immidiate response which is fine but like 0.5-1sec. later the RPM drops by a little, aaand finally the gear is engaged. At first I thought it had engaged the 4th gear but no it was 3th. When it happens, the less gas, the smaller the RPM drop and the softer the shift (I still feel that slip tho). On the other hand, the more gas, the bigger the RPM drop and the shift has this "lag" and the gear engages brutally.

This does not happen between every shift but it does happen between all shifts (1->2, 2->3, 3->4, 4->5). And happens only when the G/B needs to upshift.

Sounds like the upshift procedure is compromised in certain situations. Or something doesn't lockup soon enough.
Sometimes it's very slighetly noticable and some times it's quite brutal.

I've put the transmission in "W" mode to see if it would do it aswell aaand it did. But for the first time it did it from a full stop. This shows me that the problem can move around so I don't think it's the clutch or gears worn out. Compared to my first problem which is always between 2->3 gears, this one moves around.

I don't know how the internals of this G/B, V/B and T/C works so I don't really know how to explain stuff.

I'm actually student and money is an issue for me. I'm trying to do most of the job my self since my local dealer is a real rip-off. My dad has a good workshop and nearly all the tools I need. Without that I could sell the car right away.

What I have done so far thanks to many DIY 's on this and other forums

Buy the 722.6 transmission dipstick and mesured like 10x the fluid level on different days with the car standing on a flat ground to get accurate measure.

I drained a little tranny fluid just to have an idea of how it looked like (about 1 liter). Didn't seem to bad (dark red but not black). Then filled it again.

Checked the TCU for any fluid leaks (nothing, bone dry)

.

Checked the ECU for the same reason (nothing either)

.

Checked the Plug which mounts in the transmission conductor plate. I found a leak in the plug houseing! So I went to buy a new plug houseing form my local dealer, cleaned the plug and setteled every thing back in place. Nothing changed..

Dropped the pan, inspected for any metal or copper particles (I found clutch powder and heavily charged magnet so thats normal I guess) cleaned it all with break cleaning fluid till preflectly clean

.

Then I dropped the valve boady, got the solenoides out, checked them one by one with 12V impulsions to ensure they were clicking. No problems here. However I did read somewhere that they can be sticky and "partially" working or I don't know what. So.. not to sure what to do with that... Since my problem is on 1 shift maby one of the solenoides is to old?!..

.

Separated the conductor plate form the V/B inspected it all looking for dirt but found nothing. Looked at all contacts to se if they were dirty or anything but they actually looked very clean. Almost as if the C/P had been changed before IDK...

Opened the side pannels on the V/B (where the valves are) looking for broken springs (didn't find anything suspicious or broken). But again I'm just a random guy so I hasn't got expert eyes and knowledge mecanics have to detect failure.

Put everything back in, properly torqued and mounted, install new filter (the old filter was damn black inside probably normal though) and gasket, seal the pan and fill with fluid.
Then fluid level check till correct.

Additional info : I dont know if the tranny has been totally or partially flushed in the life of the car. When I dropped the V/B I had to put like 6L. fo new fluid back in after the operation. That makes it more than half of new oil + the 1L I did a few months ago to do fluid inspection. Let's say there is 7L of new fluid mexed with old coming form the T/C but event that didn't make even a slight difference in the way the car shifts.. To me the oil isn't whats causing the issue but IDK..

.

By the way I didn't manage to get my hands on ATF 134 so I'm using ATF 1600.

All this done and NOTHING changed..

I didn't mention I have a Valeo radiator! (I can still see the sticker) I've read these could cause problems by leaking in the transmission fluid... holy crap..
I hope it hasn't happened though! I'll have to do a glycol test on of these days anyway.

Soooo.. next steps would be??

Properly flush the entire transmission + T/C aka throw money to trash thanks to engineers not putting a drain plug on the T/C.

Or get a new conductor plate installed and programmed form the dealer ( C/P on it's own costs 350CHF) I do not know if they would install and program one I would get form Ebay.. And would it be a real genuine MB part? Always hard to say.

Maby pay a mind blowing 1'500CHF to get a new V/B and C/P together? That's without the work time and programmation of the C/P

.

Till this point it is all assumption and may not solve the problem

Sell my Benz and get a Tata GT if that even exists.

Or bring my car to the dealer and let them read whatever they can with Star before I do anything.

Anyways, before I bring the car to my local dealer I'd like to have your opinions on what should I do.. Is there anything else I can check my self?

Can MB dealer find hidden codes with Star? I mean even if I can't see any with ODB II.

I'm kind of scared to take it to the dealer.. I don't want them to tell me they want to drop the transmission because I don't have that kind of money

Oct 22, 2014 | 11:17 AM

neurodave

Senior Member

Joined: May 2014

Posts: 293

Likes: 0

From: Jersey City, NJ

2001 C320 w/ Sprt Pkg

I'd say get rid of the Valeo radiator, get the Behr unit, do a complete transmission fluid change (maybe even coolant while you're doing the radiator) and reset transmission adaptations. I keep reading on and on that this has helped most, if not all transmission issues when the Valeo radiator is present.

Also, check the transmission for codes. Those codes can only be read by a special machine (STAR I believe?), not your regular every day OBD unit.

Good luck!