older transmission b2 piston 1979
 

I wonder if you experts are still out there so many years since.
I have a 79 TD
The classic B2 thing happened to me -- no forward gears but reverse works
I have the same piston pictured and described above, with the metal seal ring.
So far I have everything out except the piston, which doesn't seem to be able to move.
Do you think the problem lies in its being stuck?
Or does the metal ring make it hard to move?
How would you advise me to get it out?

And for my sins, I damaged the yellow plastic hub cover when fiddling with the circlip. Would anyone know where I could get another like it?
Thanks
Dirk

hey starry,

i''m not sure if the same applies to your transmission, but on the 722.4 transmission, B2 piston removal was pretty straightforward. After removing the B2piston cover retaining clip, and dropping the valve body you should be able to push the B2 piston out from its bore which becomes accessible upon removing the valve body . if my memory serves me right, i was able to do so by hand.

good luck

I've stuck some pictures in this thread for the removal and refit of the B2 piston (along with the rest of the bits in a 722.118!)

http://www.peachparts.com/shopforum/diesel-discussion/304903-722-118-automatic-transmission-rebuild-monster-diy.html

If you've broken the plastic bits then my guess would be that that is game over for that part. If you're unsure you could post a picture - we might be able to help - however the general feeling here is not to add glue to a transmission environment...

My solution to your problem was to cut up yogurt pots.

Thank you all for replying. Wow. Much needed shot in the arm after a sleepless night.

I am greatly encouraged to get going and do that transmission work myself.
The car is running so beautifully and I have put so much satisfying work into it already that it makes sense to just keep on going!

It is probably going to take me some weeks too, with many mistakes and questions. The yoghurt tub strips are brilliant.

The part that I have cooked is the little yellowish plastic cup-shaped perforated hood on the outermost side of the B2 piston pictured in the very early posts of this thread. It is loosely kept in place by a circlip. I'd be very glad if anyone has one knocking about.
Dirk

http://www.peachparts.com/shopforum/...ston-front.jpg

To the best of my (limited) knowledge that part isn't available to buy separately

According to the pdf file you'll find here

http://www.ganzeboom.net/images1/ganzeboom/parts/Mercedes/722.0,%20722.1,%20722.2.pdf

...you've got to buy the whole part (number 907)

Oh by the way the metal "piston ring" (number 195 in the PDF) should in my opinion be replaced. I hope the bore in the casing has survived. To have to fix that would be interesting!

Answer
 

Guide
MB# 1152771677
No Longer Available

Boot
MB# 1152721192
$16.50




.

Did you try W.I.T. trans parts? Please double check the trans # = yours! No diagrams on their site (!) but you could call them; they seem to have everything! The entire trans case is only $100 from them! In my experience, everything that IS available from Fastlane is a bit cheaper here than from WIT.

-Tom

Thanks for the above three posts. Much appreciated. Knowing I can get the boot I broke is the best news.


I have sourced a remanufactured piston so that is also a possibility (except that mine looks good from the outside).



It will take me the weekend to pull the trans (out in the street) and the first thing I'd have to check is the condition of the bore once I have the piston out.

First few baby steps into the unknown:)

Update #1
Since my wagon is the family workhorse I have swapped in a (miraculously obtained) functional trans and now have the old one in the garage to work on at leisure.

I intend to follow the "monster diy" instructions as time allows.

hole in B2 servo
 

hi I know that this is an 13 old tread, but I will try anyway
I am working on the transmission on my wifes new old 1982 W123 300D 968000Km on the clock

and now I have a question on the hole in the bottom of the B2 servo cylinder,
is there a small air outlet hole? and in the case what size, see enclosed picture
the picture is from this tread.
in the case of my wifes transmission there is just a 5mm hole, that I think has been drilled out on previous repair job.

The hole that you are referring to is called a "throttle bore" in the Factory Service Manual (FSM). Its function is to control the rate of apply of band B2 by limiting how fast oil can escape from behind piston B2. This would be noticeable on the 4-3 downshift. There is no size stated in the FSM. 5mm seems quite large however.

In my point of view it gives not really meaning. B2 servo is a double acting servo. And its quite soft spring is trying to engage the band, and in my point of view it need pressure on the inside to disengage see enclosed picture of release port.
If you see the picture from my first post then it clearly looks like there is bottom in the hole and not a full size hole like in my wife’s case.
It is my plan to weld up the hole and then re drill correct sized small hole. Just need to know the size if any hole at all.

The cylinder bore also have damage. It is my plan to machine to 90mm and then install a thin wall liner with 88mm bore

B2 cylinder bore repair + closing hole
 

Have now worked a litle more on the transmission
I have machined the bore and installer a new cylinder sleve in the B2 servo
I machined the bore to 89,8mm and then made a sleve with a tight fit.
Now the bore is back to perfect shape again and the piston now moves freely again

Plugging hole on B2 servo
 

Have also closed the hole in the bottom of the B2 servo
The hole was drilled to 6mm
I made M8 tread in the hole and then machined a plug to fit the hole. This Way I Can also change it again if it should show to be wrong
Transmission assembled again and ready to install in car