phingoc

Hi.

I have a mercedes CLK500, 2003 modell.
VIN: WDB2093751F059077
Milage: 100.000 kilometers
Transmission: 722.633

I have some trouble with my transmission.
No fault codes stored on the transmission/engine or car, using dealer Star Diagnosis.

When i am driving in automatic mode, normal driving, the transmission is changing fine from 1st to 2nd. But when the transmission is changing from 2nd to 3rd, something strange is happening. 3rd to 4th and 4th to 5th is fine. Only 2nd to 3rd is not working properly.

The car goes in what feels like neutral, and the engine is reving up(becouse im not letting of the throttle, reving up to 4000-5000rpm), and after a few seconds, it slams in the 3rd gear.

This happens every time. Also 4th down to 3rd is a bit harsh, but its not giving a few seconds delay. All other downshift is fine.

When i drive in "manual" mode, im cruising in 2nd gear, about 40 km/h, and shifts manualy up to 3rd, same thing happend. engine revs up and slams in the 3rd gear. I can feel a harsh jolt in the car, and sometimes it is so harsh it triggers the ESP anti spin.

But when im in "manual" mode in 2nd, and let off the throttle and change up to 3rd, the transmission changes just fine, and i can get on the throttle again and drive normaly.

Also, when im heavy on the foot in both auto and manual, and give 100% throttle, the car changes fine from 2nd to 3rd. Or, it seems to change normaly, maybe a half second or a second delay, but nothing like when driving normally.

It happens in both "S" (summer mode) and "W" (winter mode).
The transmission was flushed two times, no luck. It was done at a Mercedes dealer.

I have had the car at three Mercedes workshop, one of them is specialists on Mercedes transmission here in Norway where i live. And i got 3 different diagnosis.

1. Faulty Valve body.
2. Faulty freewheel (F2).
3. Faulty clutch (K1 or K2) or faulty brake (B2).

But non of them can give me a 100% diagnosis before they have taken the transmission apart. And i dont want to spend 3-4000 USD on troubleshooting. (Yes, it is that expensive in norway). And then repair price is added on top of that. ranging from 2000 usd for valve body to 3000 usd for transmission rebuild.

So, have you had any problems like this? Or have any ideas what may be causing this issue?

(i am also posting this in w203 forum)

Rudeney

A few things to check...

If you have the Valeo radiator, it could be letting coolant mix with transmission oil. You can do a visual inspection using this guide:

http://forums.mercedesclub.org.uk/sh...42&postcount=3

Also, check the electrical connector on the transmission for oil. It;s pilot bushing can leak. It can even allow oil to "wick" into the wiring harness and intrude into the TCU (it's located under the carpet on the passenger footwell)

kb24forlife24

My car in sport mode shifts kind of harshly from 1st to 2nd gear so I use comfort mode so it doesn't do that. But sometimes I have noticed my RPMs jump about 400-500 RPM when it wants to shift but I haven't noticed what gear but it sounds similar to this problem but mine doesn't keep revving, it shifts right when that RPM shoots up a little bit. Is this a problem that I should get checked out?

Rudeney

KB24: Your My2005 CLK500 has the 7-speed 722.9 transmission. It can do some odd shifting. There is a software update the dealer can apply that will help with some of the harsh shifts, especially the jerk or clunk when it downshifts to first when coming to a stop. I have mine reprogrammed and it really smoothed things out.

phingoc

At the first transmission flush, the workshop did a "urine test" of the automatic trans fluid.. No glycole found.

Also the bushing was checked, and its fine.. (changed about 2 years ago).

Rudeney

I would still do the visual check of your radiator and if you have the Valeo. Also, check the TCU for oil intrusion - just because the pilot bushing seal was replaced and is now secure, doesn;t mean that it might not have previously contaminated the TCU with oil.

When you got these diagnoses, did they give you any of the DTCs that were stored? Knowing which fault codes they found would certainly help.

phingoc

I did check this afternoon.

I have whats looks like a Behr radiator.
No oil in the contact going into the transmission, and also, no oil in the wires going into the TCU (the ecu under passenger side foot compartment).

There was non DTC's stored in the TCU, no DTC or no events stored. The quick-test log came out clean.. just a few can diagnosis for the upper switch panel, and sunroof not initialized. Engine, trans, esp and all other driveline related came out clean.

Rudeney

Without any DTCs, how could that dealer possibly suggest replacing those parts? That makes no sense.

phingoc

By guessing, experience or gut feeling i guess. :p

Propably why i got 3 different diagnosis from 3 workshops..