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My attempt at replacing the transmission plug.

167K views 158 replies 55 participants last post by  MBGraham 
#1 ·
This afternoon I went ahead and changed out my transmission harness plug/ connector, the how to's that are around for this are pretty good but I was still not sure going into it how to remove it so I decided to snap some pics of the process.

What the underside looked like, when I first jacked up the front end.


Pull down the wire connector (fastened with a clip) to reveal the screw that holds the shield in place.


There's a star pattern screw hidden away under that harness that I just pulled out of the way, unscrew it.


Once the bottom screw is removed, simply push the thin metal shield out of the way revealing the connector.


Better look at the connector.


Twist the plastic white tab towards the bottom as the arrow indicates. The twist motion pushes out the wire harness connector.


Once its released, pull it out the rest of the way, out of the way.


This is where the problem comes from... the oil leaking into the wires, as you can see its drenched in oil.


There is a 7mm bolt in the center of the connector where the arrow is pointed.


7mm setup to unscrew the bolt.


This will allow you to pull the connector assembly out, this is i the part you'll be replacing. Closer look at the connector you'll realize that you did not have to purchase the whole connector, rather just the two o-rings that go bad over time. The connector only cost $15 from the MB dealer, the o-rings would've been $1-$2, so not a huge savings there either. The o-rings I'm referring to are pointed out by the red arrows.


Once you pull out the connector, this is what you should end up with.


The old and the new connector.


The new connector in place, with the 7mm bolt tightened.


From then on, just work backwards. The whole process took less then 30 minutes. In my situation the transmission fluid is very dark and will be replaced here very soon.

Kruso
 
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#5 ·
Thanks for the kind words guys... I have another ongoing thread in the W210 section regarding my E320 issues in which gregs210 recommended that I look into my TCM for oil. Here are some pics of what I found... hope this helps someone in the future.

This is the TCM located near the passenger side of the engine bay.


It was easy enough to unplug the left connector.


To get to the right connector I had to move the module/ block in front of it to the side.


Unplug the right connector now that its accessible.


Now the TCM slides right out. Notice the oil moisture by the right plug, that's where the trans harness plugs in to.


Closer look at the TCM.


I initially thought it was just moisture until I tilted it over. (engine bay is dirty due to being at the body shop for 3 months, needs detailing :p)


Closer look at the board, when I popped it out of the box. Notice all the oil in the background.


Another look.


I used electrical contact spray cleaner to get all the oil off of the board and the box and this is what it looked like right before I installed it.


I'll go take it for a drive and hopefully it's resolved some of my issues.

Kruso
 
#7 ·
What can changing the plug, cleaning the circuit board fix anything beside stopping leak(s)?
Correct me if I'm wrong. Oil/ATF appears to be non conductive. That's why the plug, the circuit board in your photos soaked wet with ATF but it did not electrically short anything.
 
#8 ·
ATF is non conductive, but used it carries small metal particles in it. While conductor plate is design to work submerged with ATF, the electronic boards at TCM are not.
Than I read I think Prof Lou observation that first conductor plates were made with no plastic covers what brought some problems with dirt accumulating on the relays. Later plates have plastic shields added on the top.
 
#90 ·
I guess this is why I didn't remember seeing that little cover on my car. I later reviewed a diagram and thought I might be in trouble as I had no recollection of reinstalling that part. Can this be added to earlier cars? Any parts depend on it other than the conductor plate (as far as fit?)
 
#10 · (Edited)
Thankyou for this. My transmission was replaced, and I still had a ridiculous amount of problems with it in regards to shifting and going into reverse. Before the car would not move on its own in drive...I kept getting code P0700.

The connector was changed out along with the transmission. However in regards to the TCM. The circuit board in there was more soaked than the one you have pictured, I wouldn't hesitate to say it was completely covered in fluid.

Removing the chip out of its casing took more time than the whole disassembly, cleaning and reassembly of the TCM.
 
#13 ·
AWESOME job/writeup, mercedes3!

I replaced my plug a couple of years ago and it had those same red-colored orings on the old one (Factory original). The new ones were black. How long ago did you have your plug changed with the transmission? Do you think they installed an out of date part?
 
#12 ·
hey Kajtek1 I'm fairly new to this forum and wanted to know of some good internet sites to purchase tranny parts for cheap like a conductor plate 13 pin conn. plug and dipstick I've look @ a lot and haven't found that many if you can help, thanks Ken
 
#14 ·
Hi, Ken.

Please read through the 722.6xx FAQ thread, it will explain a lot. For example, there is no such thing as a dipstick. There is a tool that is used to measure/set the level, and then it is removed and the cap reinstalled with a new locking tab. The tool is about $25-30 on ebay, or you can make one (discussed in the FAQ).

The conductor plate is readily available at parts.com, which is a good source for any OEM part. DO NOT seek out a cheap aftermarket supplier (or price) for the connector/adapter/spacer or you will simply be replacing it again. OE only on that (it's a redesigned part.) And it's cheap enough anyway even at the dealer, about $15.

Good luck.
 
#15 ·
Hello Kruso, back again just wanted to thank you for great post and the detailed pics. really grateful the step by step and good description as you went Thanks again ps where did you purchase your parts, do you recommend any web site for cheaper trans parts.
cond. plate. 13 pin connector plug, press reg spring and where to find a magnet any help would be appreciated. Oh one other thing I took my cond. plate I didn't see any cracks in it but the speed sensor module is only conn. by 4 strips metal conductor it seems awfully flimsy is it suppose to be that way. I'm trying to not replace this cause I noticed some metal in my fluid and pan, even though when I drained the original fluid I didn't see any I only put 40 to 50 mi. after I put the new fluid in and maybe 10 mi after it got stuck in elec. limp mode 2nd gear x my fingers and pray thanks again any help would be appreciated from anyone Ken
 
#18 ·
Removal of the TCM Circuit-board for cleaning.

I really appreciate all step-by-step detailed pictures, but I would like to know how to extract the circuit-board from the TCM case for cleaning. I have had the exact same problem on my 2000 C230 Kompressor so perhaps the Siemens case is different (No lugs).
 
#20 ·
I really appreciate all step-by-step detailed pictures, but I would like to know how to extract the circuit-board from the TCM case for cleaning. I have had the exact same problem on my 2000 C230 Kompressor so perhaps the Siemens case is different (No lugs).
Hi jonsager, I only replaced the conductor plate (electrics kit) which is an internal trans part. when doing this procedure you remove the drain pan, then remove the valve body, the cond. plate is attached to it. I think you are talking about the TCM which is under the hood near the pass. firewall. That's where it is on my E320 you have to check for your vehicle it may be loc. else where. If you spend enough time searching this forum you find the answer. I think you replied to me by mistake. it's easy to do, I'm just another DIY'er I've done it myself. Hope this helps, good luck

Ken
Ken, he was referring back up into the thread where Kruso discussed (and posted excellent pictures of) the fluid incursion into the TCM.

jonsager, I have not removed the TCM from the 202, so I can't tell you how MB has it restrained. Have you opened the box to simply see if yours has evidence of fluid incursion? Most often the plug simply leaks, so the TCM doesn't get flooded. So if you opened the box and there's no evidence of fluid incursion, then there is no reason to remove the TCM.

Good luck.
 
#19 ·
Hi jonsager, I only replaced the conductor plate (electrics kit) which is an internal trans part. when doing this procedure you remove the drain pan, then remove the valve body, the cond. plate is attached to it. I think you are talking about the TCM which is under the hood near the pass. firewall. That's where it is on my E320 you have to check for your vehicle it may be loc. else where. If you spend enough time searching this forum you find the answer. I think you replied to me by mistake. it's easy to do, I'm just another DIY'er I've done it myself. Hope this helps, good luck

Ken
 
#22 ·
I would doubt it the orings on the female socket that fits into the gearbox seals the socket into the electrics plate in the transmission and the outer oring on the female socket seals the socket to the gearbox casing. In theory there should be no oil in the socket unless one of the o rings on the socket fail. I would think the oring on the plug is just to keep dust water and crap out of the socket. Ive marked it in red - from when I replaced my electrics plate
cheers
Barri
 

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#24 · (Edited)
The adapter has nothing to do with leaking the tranny fluid to TCM. The funcion of those two O-rings is to prevent tranny fulid to leak out to exterior from the outside of the casing of the adapter.

The tranny fluid leaking to TCM is through the connecting pins coming out of the conductor plate and to the connector, then to the TCM.

By replacing the adapter, tranny fluid will not stop leaking to TCM.

TCM is protected by conformal coating. Tranny fluid is not conductive. I would not spray any unknown chemical to TCM to clean the tranny fluid, the conformal caoting maybe damaged by that chemical. I'd simply use paper towel to dry the TCM, or simply put it upside down to let it flow out.

I don't see how tranny fluid can leak out from the outside casing of the adapter then inside of the adapter then to TCM. The only possible path for the tranny fluid to leak to TCM is through the connecting pins from the conductor plate.
 
#25 ·
The adapter has nothing to do with leaking the tranny fluid to TCM. The funcion of those two O-rings is to prevent tranny fluid to leak out to exterior from the outside of the casing of the adapter.

The tranny fluid leaking to TCM is through the connecting pins coming out of the conductor plate and to the connector, then to the TCM.

By replacing the adapter, tranny fluid will not stop leaking to TCM.

TCM is protected by conformal coating. Tranny fluid is not conductive. I would not spray any unknown chemical to TCM to clean the tranny fluid, the conformal caoting maybe damaged by that chemical. I'd simply use paper towel to dry the TCM, or simply put it upside down to let it flow out.

I don't see how tranny fluid can leak out from the outside casing of the adapter then inside of the adapter then to TCM. The only possible path for the tranny fluid to leak to TCM is through the connecting pins from the conductor plate.
Looking at the connector itself, I have to agree with you. What then is stopping the fluid from wicking up to the TCM since the pin-holes are not fluid-tight around the pins? Because there definitely is instances of the fluid wicking up, while for other cars is doesn't happen.Is there an O-ring on the conductor plate in the transmission that seals against the connector?
 
#26 · (Edited)
Agree with gurunutkins that the single O-Ring on the male plug and TCU harness is just to keep out dirt and water.

Wish I had a photo, but recall that the conductor plate shown in guru's post is a solid cup at the bottom - with the electrical TCU leads going through a molded connection on the bottom of the cup.

The adapter plug has two O-rings. O-ring #1 is for sealing the top of the cup of the conductor plate to keep transmission fluid from filling this connection. Fluid in the cup gets wicked up the harness cabling via capilary action. O-ring #2 is for sealing the aluminum transmission case to keep fluid from leaking out. (IMHO)

See corresponding sealing surfaces on Kruso's marked up photo, and the gap between the conductor plate and the transmission housing that is bridged by the adapter plug.

And this link is just one recommendation for not buying a URO part for this application.
http://www.benzworld.org/forums/w163-m-class/1607399-transmission-electrical-plugs-beware-uro.html
 

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#27 ·
Yep as atmsmshr says the plug is totally sealed from the fluid.

the cone on the conductor plate has the pins sealed in the bottom of it, no fluid can get in from the back of the pins. when you push in the connector tube it has holes in the bottom that the pins slide through but it seals - using the first o ring - to the inside of the cone on the connector plate.
The second ring on the connector tube seals the tube to the transmission casing so the fluid cannot leak out through that joint.
that means that once the screw in the center of the connector tube is tightened no fluid can get into the connector unless the o ring leaks. Its actually possible to get the 2nd o ring leaking and get a leak from the transmission but not into the plug. Similarly if the 2nd o ring doesn't leak but the first does you can get a leak into the plug but not around the transmission. If the male oring is good at that point it will only leak up the wires of from the wire bundle.
cheers
Barri
 
#28 · (Edited)
Ah, thanks to both of the previous posters. Now you have solved one of the mysteries of life for me. :D:thumbsup:
I've asked exactly the same question when I replaced my connector, but nobody could answer it at that stage. And I hate mysteries. ;):bowdown:

PS. Mine leaked at both rings according to you description, since the cup was filled with oil and it was also leaking on the outside.
 
#33 ·
Ah, some members are actually reading something besides the forum and the W210 User Manual. ;):D
 
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