Very frustrating
 

After consulting with Marc at Sun Valley, we were instructed on how to check if the band was broken, or if the dogbone fell out. We drained the fluid and removed the valve body and found everything in place where it should be. We had no choice but to put it back together. After putting fluid back in, still no forward movement. This is very frustrating. All the hours that were spent (three different times), and hundreds of dollars in parts and fluid trying to fix the trans, and no progress. I don't know what to do now.......Rich

Sun Valley does not need any more business. They also don't need any more cores. They are very busy right now, and would not be able to get to out trans problem for weeks, even if a deal was made. They are the best for Mercedes transmissions, and they know it. Pretty much everyone here knows it as well. If you do quality work at a fair price, no advertising is needed. However, since Marc suggested the things to check, and everything looks like it is good, he may be curious as to why it still does not work. That being said, I doubt he would provide a rebuilt trans for any less than normal just to satisfy his curiosity as to why this trans has no forward movement when all is as it should be with the B2 system.......Rich

I take it you have since tried in shifting to "S" and "L" to see if there is any movement?

No forward movement is any normal forward selection. Only reverse works.

For anyone reading this thread:
Well everyone gave advice on the most frequent issues. I mean DIY sometimes is a real PITA. I am working on the Transmission from my Van and managed to bend the input shaft and do some other damage. When I worked as a Diesel Mechanic I worked in Fuel Injection and on the Engines and nothing else so the innards of a Transmission are new to me.
Learing by experience can be a PITA>

Here is what is in the ASTG Transmission rebuild manual on troublshooting the no forward motion, see pic. Note the ASTG Manual is extremely minimal and there could be stuff not mentioned that can cause the issue.

There is also stuff like the B2 band could be worn out and or the Dog Bone pushrod needs to be longer.
It is a wonder that sun valley (got my used rear trailing arms from sun valley like 9 years ago) did not tell you to check the Dog Bone pushrod length.

The 2nd pic is using a vernier cliper to check the Dog Bone pushrod for the proper length. The digram is kind of poor but I believe the Valve Body needs to be removed to do that but I am not sure.

Just double checking. If there was any movement in "S", it could be a K2 clutch issue.

Other things you need to make sure is the B2 piston bore is not scratched. Or the brake band is worn and you need a longer dog bone rod to take up the slack.


.

Remember, the B2 piston broke (common). The car was working just fine before that. I doubt the band is wore out enough to need a longer thrust pin, if it worked before the B2 piston broke.

Well just covering the bases. It could be worn and the new piston is making the connecton worst than before.

Or the brake band is somehow damaged and you can't see it until you take it out.
I think it's either the B2 piston or the brake band problem.

Nothing like a good mystery.

This is the way I look at it in general. When trouble shooting something if you don't check everything that is resonable to check and you can get at starting with the most common issues and eliminate them as a source of the issue you end up chashing your tail. Or at least that is what happens to me.

What does the Piston on the other side of the B2 Band do? I believe it is called the reaction piston.

.

To your problem and its about history of the trans ,was it reg. serviced ? Does the owner feel it maybe too expensive to go forward with a diferent transmission? Explain you are frustrated with him on the result and it may need more time to get a better value on the trannie you have in frt of you .Some bench time is the only alternative and that does mean opening it up ,$$$.You cant promise and read the future with transmissions ,they work a miracle with a tortured enviroment but are a mechanical hydraulic unit that requires a certain degree of maintience and the more you preach the less he will listen but make it known that all cases are not savable ,sometimes bad news is really all their is.,tell him the parts are being put to the best possible result but 10 or more things could be hydraulically involved ? Ive had several trannie issues , 300cd -no movement -linkage. 190d no shift after 1st -dirty valve body.300sd -no forward gears- your issue - I still havent dealt with it with much of the same issue on b2 piston behavior and results on reading other fix or fail threads,Its not always a fix.Best to see if you can get a talk with the actual shop hands that break apart these trannies and pick their brains ,the hands that open them up and replace parts to make a working unit is the brains behind the trannie shops ,the guys on the counter are counter help unless its the owner.

Yes, definitely a mystery. It was fairly easy to remove the valve body, actually easier than I thought. Seeing for sure that both ends of the band were where they should be was comforting, but NOT finding the problem is irritating. Kind of bitter-sweet. One good thing I can take away from all this is that I am learning about transmissions, things that I may not ever learn any other way.......Rich

Do you have the ability to push the car down the street and see if it will start moving? I seem to remember reading on here somewhere that you could isolate a B2 issue if you could get the car rolling, then it would shift to second and drive off.

I could be mistaken though.

I'd also be curious as to the working pressure reading.

You are as frustrated as I was when I finally found the valve stuck in the valve body by the piece of chrome plating that flaked off(see my previous post). Did you carefully check over the valve body and the tiny valves to make sure that debris from the failed piston did not hang one of them up? The B2 is downstream from the filter so any debris generated in that chamber can go to the valve body where operating clearances are very tight.. If the B2 chamber is not getting any pressurized fluid when in D, the piston will not move.

I admit this is a long shot, but you seem to have covered the more likely scenarios, just as I had.

Peter