Good day everyone.
There was a problem with the gearbox, first the error p0715 appeared and then the gearbox started shifting with shocks, sometimes it seems that it is slipping.
I changed the oil, but it did not help, I was thinking of changing the contact board, but will this solve the problem with slipping?

 

All transmission DTC codes must be cleared before test driving. You may need a scan from a tool that gets into the Mercedes codes. A simple generic OBD II code reader may not do the job.

It is possible the electronic connector at the transmission is not making good contact. It is the large connector on the forward right side of the transmission. Particularly if that connector is leaking oil I would start there. Pull it out clean it and inside the plug where it connects to transmission. Use new orings and reconnect or buy a new connector: It is not expensive. If that connector is leaking it is a good chance that is your problem if the fluid level and correct fluid is being used is all correct. Very important to only use correct Mercedes approved fluids. ATF 134 (Pentosin red, not the green, or Shell)

Are you certain the fluid level is correct; Check when in park, idling and hot.

When you changed the fluid, did you drop the pan and inspect, replace the filter? How dirty was the fluid?

A conductor plate replacement may fix your problem, but all the above should be tried first.

 

Thank you very much for your answer.

1. I have equipment that allows me to reset this code, but when I reset it, it reappears after a while.
2. I cleaned the connector, there was really a lot of oil there.
3. I checked the fluid level, it is correct.
4. I changed the filter.
5. The fluid was dirty, a little shavings were visible on the pan.

 

The electric connector needs to make good solid contact. The original orings did not hold up. You need to have a new plug with the correct orings to control the leaking fluid. As you mentioned yours was leaking badly you should lift the carpet remove the styrofoam and the steel plate ( In the USA that is at the passengers feet) and check you Transmission Control Module (TCU). It has been reported that oil can whisk up the wiring harness to the TCU and cause damage.

The fluid looks really dirty. It could have caused sticky solenoids; Only changing the conductor plate will tell if that will fix the problem and putting new clean fluid in along with the conductor plate. I'm sure the fluid you have in the transmission now by flushing through your system has picked up a lot of dirt. Best to replace with new fluid: MB approval 236.14

Wish I could be more definitive, but without further testing with DRB III on N2 and N3 speed sensor and wiring harnesses it is not possible. A good transmission shop should be able to help. Should it be found your clutch packs are damaged it could be less expensive to buy a used transmission rather than repairing yours.

Good Luck!

PS it doesn't hurt to put a magnet in the fluid pan. Mercedes sells them.

 

I will replace the connector tomorrow, I hope this will solve the problem. I checked the TCU, it is clean.
I installed the magnet.

Thank you again for your answers, I see that you are a professional.
I am from Ukraine, and we only have a few such machines in the whole country, so your help is very valuable.

 

By the way, when the car is still cold, the transmission shifts gears and does not slip, but after driving 2 km it starts to do so.

 

Unfortunately, replacing the connector didn't change anything. What should I do now?

 

Have you downloaded the Service Manual from this forum? You can find it in the TSB and How to Section, click this link: Documentation service manual
Look at the section for transmission, find code P0715. There you will find a long list of testing. This testing will take a lot of time using an electronic multi-meter as you will be testing all the wires from the transmission to the TCU and then the TCU to the PTCM. There are two wires that are CAN BUS running from the TCU to the PTCM and they are all shown in the service manual.

You can also use the search box in the upper right corner of the forum, click "threads" and choose the google option.Type in P0715 and many threads will appear for you to read.

Are you certain you are not stuck in Limp mode? Does the window in the instrument panel for the P, R, D, all show correctly?

The one thing that really bothers me is how dirty the fluid looked in the picture and you have said that it "slips" and that is why I think it basically comes to: If D0715 is the only Diagnostic code you are getting and all the wiring looks good after testing with multi meter then the only option you have is to decide between replacing the conductor plate (just parts, not including any labor, here in the States with fluid about $260 or finding a good used Nag 1 or Mercedes 722.6 transmission, about $700 from a salvaged car)

It isn't difficult to replace the conductor plate, you inserted the filter into it when you changed the fluid.

With a transmission swap you need to get the car up in the air so there is room to drop the transmission down and out of the car. If you swap transmissions you should replace the rear main seal AND the plate it sets in. Of course you can also pull the engine and transmission up and out from the front, but that is more work, more time consuming and expensive as all fluids must be replaced. Spend the time looking trough the service manual and reading the search threads before making that decision. GOOD LUCK!

 

Thanks for the advice.

Interesting fact, when I reset the gearbox settings it doesn't slip and drives fine for about 10 km. and then it starts slipping. Why is that?

 

The fact that it drives fine when cold indicates the TCU and the PTCM with the wiring harness is okay, but please look through the troubleshooting pages in the service manual.

However, there is no definitive answer to your question. When the transmission and fluid is cold it may be able to put enough pressure on the clutch packs and they work Okay, but as the fluid gets hot it can't maintain enough pressure on those clutch/metal interface plates and so it starts slipping. The same reasoning applies to the solenoids; the heat is causing the solenoids on the conductor plate to malfunction and those solenoids control the clutch packs shift points.

The clutch packs consist of fiction plates with smooth steel plates between them. The number of plates varies between gears and I think the SRT6 transmission has more plates than the Limited models. Looking at your picture with very black fluid those fiction plates and steel plates were slipping to the point of causing so much heat the fluid burned. The friction plates may be damaged to the point they must be replaced. Without opening the transmission it can not be actually determined how bad they are. You can try to install a new conductor plate (be sure it comes with new solenoids) add new fluid, new filter and the transmission may work okay. You can only give it a try and hope for the best.

 

He should refer back to post #2.

 

So, after analyzing all the information, I decided to first flush the board and solenoids, the next step if that doesn't work is to replace the board and after that, possibly replace the box.

 

Good afternoon everyone. Today I removed the board, there is a little oil in the connector again, I changed the connector earlier. Strange.
Maybe the problem is in the board in the connector?
I ordered a new board.
Question, how to check the speed sensors, what should be the resistance there? Are there other methods to clearly diagnose the board?
Do I need to flush the solenoids and the hydraulic unit?And how can a gearbox slip with a bad board? Has anyone had this happen?

 

Thanks to everyone who helped, especially zip439. The problem is solved.

 

Thank you for the update. I'm glad that you have resolved the problem!