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B1 Piston O-ring Replacement?

3K views 13 replies 4 participants last post by  Anovak 
#1 ·
I have a leak at the bottom (see pic) of what I believe to be the B1 piston cover (my transmission is the 722.306). This is of the driver's side of the transmission (btw,not my transmission but a pic of one that looks very much like mine). What is the procedure for removing that cover? Is there anything to be watching out for? And, what O-rings will I need to replace to stop the leak?

Appreciate any help in advance.
 

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#2 ·
Here is what I found in terms of a diagram of the "Pressure Body B1" and I am hoping someone can confirm from their personal experience of working on these that I'm looking at the right thing and also what to expect when pulling the cover plate (screw plug) off.

I see two o-rings in the diagram (see attached image, #31 and #32) and am also trying to confirm that these are indeed the two listed on AHAZ:

http://www.autohausaz.com/pn/0059978648

http://www.autohausaz.com/pn/0059978048
 

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#3 ·
722306 EPC

Anovak,

I have not worked on that transmission but I did have a look at the EPC because I was curious. I think the seals you are asking about are parts:

A 005 997 80 48
A 016 997 34 48 replaces A 010 997 08 45

The other part you asked about, A 005 997 86 48 seems to be the large seal on the B1 piston in the assembly on the passenger side of your transmission. AutohausAZ sells the two parts above.

http://www.autohausaz.com/search/product.aspx?searchtype=partnumber&partnumber=0059978048&searchbutton.x=30&searchbutton.y=8

http://www.autohausaz.com/search/product.aspx?searchtype=partnumber&partnumber=0169973448&searchbutton.x=22&searchbutton.y=9
 

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#4 · (Edited)
Thanks, Brad. I'm a little confused. Looking at the diagram you provided, I am not seeing the large cover plate (referred to as "screw plug") on another diagram. As you can see from my picture in the first post, the green arrow points directly at the bottom of this plate and it has a recessed, large hex opening in the center of it. This is where the leak is coming from, the very base of the screw plug, and I am looking to find which gasket resides behind it so as to replace it and hopefully stop the flow of fluid out of it. Do you have any way to determine exactly which o-ring might be behind it? Appreciate, as always, you kind assistance.

PS - If you have another look at the attached image (image001.jpg) in post #2, you can see the "screw plug" (#35) and what appear to be 2 o-rings, #31 and #32. Those are the ones I'm thinking may be the culprits but unfortunately, there are no identifying notes with part numbers for them.
 
#5 ·
Had my 722.313 transmission out and replaced all seals I could get to, bought a full MB kit. Nothing special to replacing the seals. Used a needle to get some of the seals out of their groove. The kit did not include the kickdown solenoid seal, and not the gear shaft seal if I remember correctly.


I made one mistake when bolting the transmission to the engine: the primary pump has two small nobs that need to be properly aligned with the input shaft. This is easy to verify if you check the distance between the flywhell and the housing before removal. On my transmission there is a plastic plug that prevents the TQ from falling out during disassembly, the TQ clears this plug with about 5 mm when installed properly.

My car ran normally, except leaking ATF for nearly 20,000 km, before suddendly I had no drive in any gears. Turned out both primary pump tabs had broken off causing total loss of pressure. Fortunately this was in my driveway, but the engine and transmission had to come out again and a new pump purchased (nearly $1000 from the dealer)
 
#6 ·
Thanks for your comments, hchaugli. I would again ask, do you remember replacing the seal/o-ring at the location the arrow in my first post points to? I am still not sure exactly which seals to order and I really think, at least for now, that this is the only one that is exhibiting a leak. On the diagram I have provided in the link it is called the screw plug and part#35.....I just need to know which o-ring to get to stop this from leaking.

Beautiful part of the world you live in, was there in 1976 for a few weeks and found it literally intoxicating!!! Some of the most friendly people as well.
 
#8 · (Edited)
Danke schön, mein Freund! That was what I was waiting to hear! I kind of thought there may not be an o-ring right behind that plug but was unsure. I will order the two Brad mentioned (many thanks again, Brad) and replace the old ones with them.

When one pulls that plug, does the valve (pressure body) just slide out or is there a special way to proceed? I would imagine needing to take it out to get to the o-rings for replacement?

So appreciate all your help....
 
#9 · (Edited)
When one pulls that plug, does the valve (pressure body) just slide out or is there a special way to proceed? I would imagine needing to take it out to get to the o-rings for replacement?

So appreciate all your help....

Yes pulls straight out, I use a strong flex head magnet, but you should be able to
grab it with needle nose pliers. The pin will probably come with it.
It's keyed so you can't put it in wrong.






Fish
 

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#11 ·
By the way, I believe the B1 piston is on the other side of the transmission, my notes say that the B1 reaction valve is behind the plug.

Seals cost next to nothing, so I buy all in sight when in doubt.
Benzsource points out that the shift lever is often a source of leaks in this transmission, so probably a good idea to replace whilst you still have access.
 
#12 · (Edited)
Hchaugli, that is correct about the B1 piston being on the other side.....still learning about this and we're talking about the side where the valve is. Also, might you be able to tell me what the part number is for that seal on the shift lever and what is involved in replacing it? Does it just pull out like the valve behind the plug on B1? I haven't ordered anything yet so will include that if you can give me the information. Thanks!

Did some research.....is this perhaps the part you are talking about?

http://www.autohausaz.com/pn/0069970147
 
#13 ·
The seal looks right, it is item no 256 on the EPC figure. MB part no: A0069970147

Here is the procedure for replacing the shift lever seal:
-Remove the shiftshaft lever
-Remove the neutral safety switch (2x 10 mm bolts)
-Position the transmission with the valve cover up.
-Remove the oil pan
-Remove the oil filter (3 Phillips screws)
-Remove the blade spring (10 mm bolt)
-Remove the 5 mm Allan screw locking shift shaft
-Pull the shaft out
-Pry out the seal
-Replace the seal
-Re-install the shaft
-Mount the Neutral Safety Switch, finger tighten the 10 mm nuts
-Mount the lever
If you have not done so, replacing the lever nylon bushing is not hard, two are needed. I heated them in boiling water to make them pliable to ease mounting.
-Set the shift lever to neutral position. The gear positions on this lever is opposite what is in the car (PRND32).
-Insert a 4 mm drill bit through the switch hole and into marking hole on switch. Tighten both 10 mm nuts. Tighten the shift lever mounting screw (10 mm)
 

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#14 ·
That sounds quite workable.....now if I hadn't just changed transmission fluid a short time ago!!! I think I'll get the part and then wait until I see some evidence of leaking. The o-rings at the valve can be replaced without draining the fluid so they will be what I fix first given that there is already evidence of leaking there.

Thank you so much for the tutorial and for taking time and effort to help me with this. I much appreciate it.

Maybe a stupid question, but I'll ask anyhow. Does anyone here ever drain the transmission fluid and put it back in when finished working on it, or is it a start-over, get new fluid every time? I was just wondering because if one could fashion a very clean basin in which to catch the stuff, having just replaced it, would that be ill-advised? I'm aware of the persistent warnings about cleanliness with these things, but how critical does it have to get?:|
 
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