i have seen several of these trans get fluid in the computer because the big plug that plugs to trans at top right is getting fluid in it from a bad conduit plug.those conduit plugs are cheap[less than $15] and come with new o rings to stop the fluid leaks.good check is to take off protection plate and just look at plug and surrounding areas.just a small area of dampness will indicate a leak as will a wet mess but the latter is rare.these trans also suffer from the electrical board inside trans getting fluid contam and will cause limp mode.the elect board is relatively cheap[about $200] and i bet local dealer has several in stock.

I'm permanently sceptical of anyone who suggests that ATF will irrepairably damage a PCB.

If it were in front of me, I'd be spraying isopropyl alcohol onto it, and drying it off completely, before buying a new one.

I too would try spraying with CRC electronic component cleaner, readily available at AutoZone. Why not try the cheap route before investing more $$$ ? However, the possibility DOES exist that the fluid can cause some damage. Electronic components, resistors, etc. are delicate and these boards were not exactly designed to run in a bath of ATF.

Try pouring some on your paint job and cleaning it off with alcohol. :)

What are you doing bringing a car like that to a "transmission shop"? Of course they are not going to tell you whats wrong because they don't even know whats wrong. All they do is swap parts until the car works again. Thats not exactly the place you want to take a car that has a $5000 transmission.

No thats brake fluid :) Oil doesn't do that much to paint :)

Then why not try it. Will probably take you a while to get it all cleaned up.

Honestly in most cases the mechanic knows that the amount of time that it takes to correctly clean the part of all contamination is not really worth it to his bottom line. Not to mention having to go back in if he did not clean it well enough. The advantage you get as a consumer from having this done is having your transmission fixed one time and knowing its repaired. With the labor involved in cleaning the board the price would probably be very close to the same. Your saving your mechanic a ton of time and giving him a little profit off of a part sale thus keeping him in business to repair your car again in the future. If you went to the dealership they would just want to replace the whole transmission to the tune of $5000. There is cheap but then there is self defeating cheap. :)

Hi,

Should give you some back round on car. the car has 150k miles. the valve body plate assembly was repaced about 10k miles ago.... and the selonid was replaced when car stuck in first gear. the tranny computer in question is underneath passenger foot well. Just wondering if its worth replacing the computer to see if this solves the issue. What codes should I look for if in fact it is the tranny computer.

thanks!!

On my 722.6 my mechanic suggested replacing the plate and the valve body itself. My 1999 model car had the latest version of the firmware so I did not have to replace the transmission computer. I had the trasmission computer wiring harness and a some mechanical bits in my shift assembly replaced at the same time. My car drove perfectly except for a few bad shifts here and there when I brought it in. I had all the suggested work done and have had flawless shifting and performance since.

I would not "throw parts" at this type of problem. Go to someone who has a real star diagnostic computer and find out what's really wrong. Guessing only delays the repair and can cause more damage.

The transmission shop had it hooked up to a computer and pulled the transmission computer. Said it needed a rebuilt unit and computer.

My problem is the shop did not discuss what was actually wrong. Would a tranny that doesnt shift out of first gear, and reverse works , need a total rebuild??

Will the codes give me a good indication if I really need a rebuild, or just a computer or valve body assembly??

Thank you again!

Here's the problem "the transmission shop" and "the computer". This is a Mercedes-Benz not a Chevy or a Honda. If your not dealing with experts (an MB trained mechanic) your dealing with people who have general knowledge. These cars are highly specialized and don't work like the Chevy's and Honda's that the are common on the market.

Take your car to someone who specializes in Mercedes ONLY and make sure they have a Star Diagnostic computer!!!!!!! Even a highly advanced general automotive computer won't read a lot of the codes in the 722.6 transmission. A Star Diagnostic computer can read how much the transmission has adjusted itself to compensate for the wear on your friction material and its able to reset and reprogram certain settings within the computer. Without knowing exactly whats going on your wasting your time and money attempting to do any repairs on this car.

Its likely that the shop did not want to discuss anything with you because they did not want to empower you to make your own choices and take your business elsewhere. I'm sure you even paid them for their "advice" in a diagnostic fee. Whatever you do DON'T go back there and even consider letting them do a replacement. You have no clue where the transmission came from and often they are cheapie rebuilds that fail shortly after the warranty on the transmission runs out.

Get a phone book and start looking for Indie MB mechanics (the dealerships are just as bad as the "transmission shop"). Find one with a Star Diagnostic computer and who has dealt with the 722.6 transmission. Ask questions and expect honest answers. If you don't get answers take your money somewhere else. I have two really good indie shops that take care of my Volvo's and MB's who I trust. I wish you the same luck in finding someone who you trust to keep your cars in tip top shape.

there are a couple of weak bearing assemblies in that trans and if there is evidence of problems[in the pan]with either or both if it's just made to work without addressing those problems the fix could be shortlived.

David,

Do happen to know the part number for this plug?
(and I do not quite understand the location of it either...
is it on the trans side or computer side?)

br,
syljua

it's on the top right corner of the transmission,right at the back of the bell housing.there is a plate covering it,one or two screws to get off.btw take out trans computer and leave standing plug side down on white paper overnight.if it has fluid contam you will see the stains on the paper in the morning.

Good idea, I'll try that tomorrow. ..Well had a mechanic friend with a fairly new scanner pull some codes from under the hood.
first one was the P0730, the other two were mercedes transmission codes. 55, and 151

55 was descibed as gear ratio not reach, the other code was target gear not reached. Cleared out the codes for now.

Still trying to track down an indy shop that has experience in this area and proper equipment.