300TD B2 piston replaced, still no forward movement
 

My friend brought his TD over with no forward movement, and was told it had a bad B2 piston. He provided the new part, and I read a few threads on the subject. After removing the cover (real hard job with the limited space), I found the B2 to be in pieces. http://www.peachparts.com/shopforum/...1&d=1494382089
I installed the new B2, and put everything back together. After filling up the fluid to the proper level, it still had no forward movement. I did more reading, and thought that maybe the bushing and/or seal was bad. I procured the parts, made a puller as described in another thread, and pulled out the old seal and bushing. I installed the new bushing and seal, making sure the seal was installed properly. After replacing the filter and gasket and putting everything back together, it still has no forward movement. It is kind of discouraging doing all this work with no positive results. Yes I did use grease to hold up the "dogbone" so it would be in the right spot on the brake band. Anyone know what could be the problem? Thanks in advance, Rich

EDIT: Reverse gear works fine, both before and after B2 replacement

Hmmm, I would start by pulling a transmission cooler line and making sure that the pump is working.

X2

Reverse gear works fine, so I am sure the pump is working.

Was there tension on the new piston when installing it?
i.e. the piston is being forced outward.

If it slid in freely with no tension, most likely the brake band it toast. You'll need to overhaul the trans at this point.

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Sherry ex had a similar problem with his w124 and turned out to be something (broken spring) in the governer.

Forget that thought he had 1st gear
http://www.peachparts.com/shopforum/diesel-discussion/380228-whats-likelihood-valet-ruined-my-transmission.html

Yes there was spring tension against the band before putting the piston in, and also afterward.

Check the pressures. If they're ok, the most likely explanation is that the band itself it toast.

This is a long shot, but many years ago I decided that it would be a good idea to replace the original B2 piston in my 83 300TD with the newer design in order to avoid the problem. To make a very long story short, I used a chrome plated socket to tap in the new seal and bushing, a flake of chrome came off the socket(despite my efforts to keep things clean) and lodged in the valve body where I eventually found it wedged in by one of the tiny valves, causing the B2 piston to become inoperative in somewhat spectacular fashion(noisy) resulting in a tow home.

If the failed B2 created any tiny pieces that could have been carried away in the fluid, this could happen. I don't know if you can check for fluid flow to the B2 piston cavity with the transmission in drive and the motor running, but that might be easier than dropping the valve body for inspection.

Peter

I second the though of the band being an issue. When these problems happen and you do the b2, it is usually a bandaid. Eventually you will get reverse issues, flares, slips etc. I've learned when one thing goes wrong, pull it all and rebuild it. These trans are cakes. I could have one done in 30 minutes on a bench. Getting it in may be a little longer!!!

There is an old style metal bushing (replaced by a Nylon one) and a lip seal that also should have been replaced. The lip of the lip seal faces outwards which is contrary to the way you might think it goes.

But, I have never read what happens if you get the seal in backwards.

Can some one verify this. I think that if you remove the Pan there is a tiny area where you can view that Pin (Dogbone) where it goes into the Band. If you can see that you might be able to get something in that and see if the Band is loose.

I pulled the cover and replaced the bushing and seal (described in the first post), after I replaced the B2 piston, having the same results. Again, yes I put the seal in properly. I suspect there was nothing wrong with the original bushing and seal, as replacing them did not fix the problem. I also looked to see if the dogbone was in the right spot, but it appears the valve body will need to come out to see up inside......Rich

Dieselgiant describe having to do a do over ,if this is any help he has it on his site.

For anyone interested this is a quote from the Diesel Giant site.
"Because I was too lazy to remove the pan to insure the push rod was secured into the B2 piston properly. I got the car stuck in the street in because it would not go forward. Getting 3 of my neighbors to push my car back into the driveway and up the ramps was a little embarrassing. Please learn from my errors."

The below is without revmoving the valve body.

"Looking up into the transmission you can barely see the brake band to the left of the brown plastic piece. You will need to look at this after you install the piston and push rod to ensure the push rod engages the brake band. I did not do this simple step the first time and caused me to do the whole job over."
For more info on that you can go to the site (I am not recommending buying parts there).

I believe I also read back in 2008 where someone claimed that they did not get the Pushrod in the right pisiton and it broke the B2 Band but my memory is ver hazy about that.

Note that in the picture apparently due to the camera angle (?) you cannot actually see the pushrod/dog bone. And I can't remember what I saw when I did the job.
But it is nice to know there is a way to verify without removing the valve body.
Note I edited the original pic trying to lighten the shadow.

I'm guessing the dog bone fell out as you put the piston in. Just a guess.

The other possibility is a broken band.

I know, it was all mentioned and you checked tension. But it sounds like it has to be opened again.

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.

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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

Well you know more then me. I have only done the B2 Piston job and of course fluid and filter changes.

The various valve springs inside of the valve body have been known to break.
But, as you said it is too the point where you are expending lots of time on the issue.
I am stuck on a transmission issue like that with my Van. I have the genuine Chevy service manual and there is nothing in the Manual about what you need to remove before you pull the Pump off.
With a lot of difficulty I got the Pump off only to find that there was 3 items sticking through the Pump that should have been removed that I sheared off. That is right I unknowingly cut off all three. A steel tubing, a kick down solenoid and and the neck of the Filter.

I damages a bushing and bent the input shaft. That is all the damage I know about so far.

The only good news is that I found loose bushing in the Pump.

I have been fooling with that for a couple of hours each day for 2 weeks.

It is looking like by the time I get the stuck bent input shaft and drum out I am 1/2 way towards a complete rebuild.
Anyway I feel your pain on the transmission issue.

I'm starting to like the theory that some pieces of the B2 are jamming up the valve body or some other critical piston.

This sounds tough. I fixed my B2 and it looked just like yours. My trans died 1.5 years later with some really hair raising temporary failures on the way (freewheeling in hot stop and go traffic). Finally I took the car to Marc at Sun Valley and got a new trans. It was the best money I ever spent. That car rocks now. I wrote about the experience in the forum.

Yes, they are super busy. It is a seller's market because it is a great price for a great product. You have to just wait. But OMG I love my new gear box. Worth every penny.

Marc mentioned to me that people do a B2 and get a bunch of debris in the trans. This can lead to an early death after doing the repair.

Good luck. You seem to be having bad luck. There is another possibility...what you were told about the original running condition on the car may not be factual.

Basic question: is this particular car set up to start in 1st or 2nd? You may have a problem with the B1 piston. You can force the car to start in 1st by applying power directly to the solenoid.

It's a 1st gear start.

Well, I guess the trans has to come out. Marc at Sun Valley said to bring it in. It may not need a rebuild, and we are hoping something simple is wrong. There was no metal in the pan when I took it off the first time, so that is a good sign. The fluid did not look or smell burnt either. I will keep everyone updated.......Rich

Update:
 

I took the trans out, and it was brought to Sun Valley. They took it apart, and fixed something (not sure exactly what). Supposedly they tested it and said it works fine. Today we installed the trans. After topping it off with fluid, it is doing the exact same thing. It works fine in reverse, but still no forward movement. It is getting very frustrating. A lot of labor has gone into this car with zero positive results. I am not sure what to do now. I am hesitant to work on it any more........Rich

Rich, I feel for you. Does not look like thing is going your way. The brake then the tranny. I have nothing to offer except encouragement.:eek:

And what does Sun Valley have to say about their work?

I don't know yet, I will find out today maybe.

Did they test your torque convertor as well?

As stated several times, reverse works as it should. I would think that the TC is working properly.

They said to pull the valve body and bring it in. I can't see how it could be the problem. It was easy enough to take out. I hope they have some hocus-pockus magic to work on it.

Oh man. I wonder what is going on. Looking forward to hearing good news.

When I was doing some searching their seems to be an issue of 3 bolts that come loose at the pump ,you have to take the transmission down and pull the housings apart to see this ,but it is doable .If during assemble that their was no loctite used on these 3 bolts they can come loose or fallout ,these force the two plates together,trans fluid being the hydrauilic loss hear.I remember stretch had commented on this thread ,it was an older one .

HERE IT IS http://www.peachparts.com/shopforum/diesel-discussion/333601-torque-converter-transmission-problem-82-300d.html

Sorry, I forgot to post the final outcome
 

I looked back and found that I didn't post the final outcome. It was in fact a bad valve body. I pulled it and sent it to Marc, and he provided a rebuilt one. I put it in and the trans goes into gear, and shifts perfectly. Yes this was over 5 months ago, and I am sorry for letting everyone hang for that long.....Rich

How was the valve body bad ,just curious ,loss of forward gears with reverse still functioning is a common trannie issue it seems ROLLGUY .The question of the b2 piston being the issue usually rises to the top . The expert transmission guys only find the issue after taking it dwn then inspecting it further . Heartache comes when we find out we cant fix it as a diy and part of that hurt is in the pocketbook.Is the valvebody another reality to the symptoms .I have talked to an expert across the issue and he says once the pan is dwn he can tell if the b2 piston is the issue , and he has owned one or two.Ill reckECK this as it might need to be the final say so for b2 piston removal ,take some clear pictures of the spot to look at my trans with this current issue, post with pics to this thread hopefully in Jan .when I can spend time on this one car.

I wouldn't have believed it if I didn't experience it first hand. After getting the trans back from the shop, installing it, and it having the exact same issue was very discouraging. I thought afterward that surely if the VB was suspect, they would have replaced it when it was at the shop. Evidently, they were as much surprised as I was that the VB was bad. Although it was a lot of discouraging work, the final outcome was a big relief.....Rich

Perhaps this video may capture the b2 piston and itshttps://www.youtube.com/watch?v=LIr99-2IpFs connection to its band .