eight8

Hello... Does anyone has issues with the 7 speed transmission?

I have a 2004 (manufactured in late 2003) S500. When transmission has completely cooled down, the 1-2 and 3-2 shifts are very harsh. Sometimes, the 1-2 flares as well.

But once transmission is at operating temperature, all the shifts are smooth as butter. But sometimes (very rare), the 1-2 flares even at operating temperature.

I sent the car to the mechanic. He flushed the transmission, filled with new oil and replaced the filter+gasket.

The harsh shifts went away but came back after sometime.

So, I sent the car to Mercedes and asked for a software upgrade and a transmission adaptation. They told me that there are no upgrades but they did the re-adaptation thing. But it did not solve the problem.

From what I know, my car is not contaminated by glycol since it has the 7 speed transmission. And there are no error codes on the STAR module.

I would really appreciate if anyone could help me.

Thanks!!!

cybertronicify

That is a very common problem with the early 7g tronic transmissions, check to see if coolant is leaking into the transmission fluid. These cars use the coolant to heat up the transmission fluid so that they operate at the same temperature, and if coolant is inside your transmission, it will cause the hard shifts.

eight8

From what I have been told, the 7 speed transmission (722.9) does not have this coolant problem. But I might be wrong

I did a lot of research and noticed that only cars with the 722.6 transmission may be affected with this coolant issue.

cybertronicify

I'm not sure which radiator you have, but only the Velro (i think thats how you spell it) one is the problem. But it can well be your torque converter clutch not engaging or releasing in time, making a shift like clunk.

BTW when you say cold, do you mean Southern California weather or Alaskan weather?

eight8

I am not sure which radiator my car has. I have no idea where to check the reference and brand on the radiator

I can see "Behr" on the engine front fan. But it is a totally different auto part.

When I say cold, it does not mean Alaskan weather. haha! I live in a country where the temperature is always hot! Coldest temperature is 16 degrees.

cybertronicify

16 degrees F is pretty cold thats below freezing. Should be normal when your car doesn't run very smooth, but from a far away opinion, i'd say your torque converter clutch is not releasing in time, thus making a clunk which you interpret as a hard shift.

BTW when you say you start in 1st gear, are you in SPORT mode? If so, the TCU holds the revs and shifts faster. Try putting it in WINTER/COMFORT mode and see if there is a difference.

eight8

Sorry for the confusion. I was saying 16 degree celsius (60 degrees F)

I tried in comfort mode but no difference

mrbobby

The first thing you need to do is have the transmission read

by a STAR system. Unless I miss my guess you will find some of the information you require. The early 722.9's were rife with issues. A number of them require new valve bodies (I recently had one installed in my 2005 CLK 500) to repair the symptoms you mention. Having said that I find that even with the new valve body ($2000 +) the transmission is still not the best I have ever had. I'm even considering selling my cabriolet because of the annoying transmission.

Sherbet dab

Try checking battery is ok, if in decline it causes a similar problem

eight8

So here is the story...

My 7 speed Mercedes used to have rough shifts (1-2 and 3-2) only when cold.

From "cold", I mean when the transmission is cooled down like first start in the morning. I do not mean freezing temperature.

I was away for 2 months and my dad drove the car meanwhile. He is a slow driver and I am not.

When I came back after two months, I noticed that the car STOPPED having rough shifts when cold. I was so glad that the problem solved by itself!

But I was wrong..... After 3 days driving the car, the problem started again.

I believe that this is because the transmission has adapted to the way I drive. Like I said I am a fast driver but my father is not. So, maybe the transmission fails to adapt properly to fast driving?

I don't believe that there is a mechanical failure. The very rough shifts would not have stopped although my dad was driving if there was really a mechanical failure.

I would appreciate to know what can be done to solve this issue.

Thanks