For those that have done a B2 piston repair, I have a question.

Did you have to replace the entire piston or is it possible to replace just the bushing from the metallic style to the nylon? Will the nylon bushing fit the original B2 piston?

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Sam

84 300SD 350K+ miles ( Blue Belle )

I have not read anyone saying the Nylon Bushing will not fit the old Piston.

The Nylon bushing is cheap and you could pick that up at the Mercedes Dealership. You could buy it at the dealership and try it out on the B2 Piston and compare it to the Aluminum Bushing.

Deliveryvalve said that he and a friend of his went to the Junk Yard and removed that later updated style B2 Piston from a later model vehicle and were charges something like $6 for it. You would need to ask him for details on that.
On the W123 the B2 is harder to get at then it is on some of the other vehicles that use a simlar transmission. That makes it easier to get one at the junk Yard from a non-W123.

The also used to sell the outer Teflon(?) Seal that is on the Piston as a seperate item but I have never read of someone doing that.

When I did mine I replaced the Piston and at the time I bought it it was $106 for the B2 Piston itself; but that was over 4 years ago.
Get the Part number and shop around for a decent price.

Considering the hours to do the Job and what can happen if the B2 piston Breaks I don't think I would consider reusing the B2 Piston.

It does look like the B2 Piston grabs on the Aluminum Bushing but I have not read of that being a definative cause of the Piston breaking. There could be more then one factor involved.

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84 300D, 82 Volvo 244Gl Diesel

I would not reuse the original style piston. The original part number has now been superseded twice, which says something right there.

You have to do the entire job just to change the bushing, anyway, so I don't see the point in putting back a potential liability part as a failure can sometimes take out the B2 band.

I would suggest you put a 'want to buy' ad in the used parts subforum and see if someone has a new style B2 piston used. I went that route. Then went to the dealer for the bushing and the seals.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

So you are saying the piston itself (not the nylon bushing) has been superseded twice? Or is this for the entire assembly?

Is the piston nylon as well? If it is, I can see why you don't recommend reusing then. I wasn't aware that there was a possibility of it breaking. I had only read about the metal bushing wearing and then binding.

Thanks for the information guys.

The symptoms I'm having is a major 3-4 flare. It's getting worse to the point of having to manually downshift and wait for a decline to shift up. Once it finally shifts to 4th it will stay there until I slow down. Then I have to repeat the process.

From what I've read, B2 piston and K1 spring are starting points.

Yes the piston itself has been superseded twice, according to my dealer parts manager when he was looking stuff up for me.

Anyway, I was under the impression that the main B2 symptom is slow engaging D from P or N. I was not aware it was a factor in the infamous 3-4 slippage.

Have you checked that everything is 100 percent on the vacuum side? If your rubber connectors are old they will be leaking more than you might think and you could try to adjust the vacuum control valve (VCV) a touch to see if that would help.

Just throwing out ideas.

But for sure if you think your B2 is the original spec, I would do something about it. I ignored it and ended up with a dead car in the driveway. I have had these cars since 1997 and I can't believe I have read so many B2 miseries on the lists and forums I have been on... yet just lived with longer D engage times and let it get worse to where it failed.

I certainly Homer-ed that one. Don't be a Homer .

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

What he was saying is there is the Piston that came with the Transmission when the Car was made and then there was 2 other Pistons made trying to fix the breakage or other problems.
When you buy the newest piston you get the one that is least likely to break or cause other problems.

The new Piston is not nylon. However, they all have a Tefolon or Nylon outer ring on them. I don'tnow what material that ring is made of.

It is your Car if you want to reuse the Piston you can. However, if it breaks anyway be sure to post back on this thread so that we can prevent the same from happening to others.

The replcement of the Nylon Bushing for the Aluminum one is the only change I know of on that.
Also remember which way the lip on the Seal faces so the new one can go back the same way.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

Hi - I know this thread is a year old but I have a specific question regarding the lip seal on the B2.
We are having tranny issues on our journey from Nova Scotia to Argentina - currently in Guatemala - we are in a vehicle with a OM602 and a 722.3xx tranny. I was in the tranny changing the B2 actuator pins and thought I should replce the Lip Seal that the body of the B2 piston sits in - I ordered the correct part number for our vehicle and had it confirmed by Mercedes UK.
BUT - before I wrecked the old one getting it out I thought I should probably try it for size over the now removed B2 piston. Even with the correct size socket -32mm- I could not get the seal to slide on to the piston at all.
So I didnt remove the old one! and had a play with the piston in the old seal - in situ - wow it slides in real easy - I mean no feeling of tightness at all the piston just runs straight through the seal easy as you like.
So as the oil pressure in the piston is what actuates the B2 system and therefore 1st and 2nd gears I am thinking that IF the seal is leaking under pressure then the engagement of low gears will be reduced in efficiency.
======================
So My question is to anyone that has replaced/removed the B2 piston - when re-installing the piston (after vasoline on the pin in to the brake band divet) should there be some resistance to getting the piston through the seal?
The seal that is currently installed is a simple plastic and rubber lipped seal
The seal that mercedes sent me is lipped yes but it also has 2 ridges of rubber that the piston should mate with AND it has a locking spring band set in to the lip on the piston side of the seal (like on the side that is closest to the outside world) - the old seal installed doesnt have that ring - or have a groove for one to sit in.
The B2 piston that we have has the teflon edge and the insert in the tranny is plastic not aluminium - the part number of the back of the piston is 126 277 11 38- the seal we just bought is part number 006 997 73 47
So I know that the B2 has been redesigned over the years and I wonder if the the seal I now have is for a different version of the B2 piston and if so how on earth am I going to get the correct seal for my piston without being down the road from MB dealership?
Any help anyone?
Regards
Mark and Saskia - still in a field in Guatemala.

Was your original piston broken?

I am assuming you are not speaking of the white nylonish/teflon seal that goes on the outside of the Piston.

When I did mine on my W123 all of the parts were well documented by others doing the same job so I was absolutely sure the black lip seal was the correct one.

I never tried it on the part before I instlled it but it is normal for there to be some resistance or it would not seal. I can't comment on how much resistance is normal.

I used an new bushing and black lip seal (on mine the lip faces outwards). I did have some difficulty installing as the Piston does not want to go straight in till it is inside of the seal and futher in the bushing.
I used STP on the piston end that goes into the black seal and also in the large piston bore in the trans casing.

All that being said I am not for sure that your trans and mine have the same parts in that area.

This is part of what is in my notes (W123) and I don't know who wrote it to quote. (speaking of the black lip seal) The new lip seal (006 997 73 47) then goes into the bore - lip facing outwards - to hold the plastic bushing in place. It's then obvious that the plastic bushing is what locates the small polished end of the B2 piston in the center of the bore; the lip seal's purpose is only to prevent trans fluid leakage from the bore into the area where the B2 band and apply pin are.

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84 300D, 82 Volvo 244Gl Diesel

Contact Sunvalleymercedes@gmail.com

Website: mercedesdismantlers.com

Marc is the absolute expert on anything related to a Mercedes automatic transmission.

HI Diesel911
Thanks for responding so quickly.
So I reckon that I have the b2 piston from 1993/4 and that there has been a change in the seal and piston since then. So the newer piston and the seal I have would be correct for each other.
From your description I would have been able to push the new lip seal over the piston 'on the ground' and as I couldn't - that the seal I have and the piston that I have are not exactly matched.
The original piston is not broken - we are having issues with climbing steep hills here in Guatemala and by diagnosing the symptoms it was decided to dismantle the tranny to measure the play in the B2 piston to absolutley determine the correct length of actuator pin we should be using - as it turned out the play we had was 7.9mm with a 47.2mm pin - i ordered all the pins from MB and ended up fitting the 49.6mm pin.
That was why I was inside the tranny and the b2 piston.
It was a forum comment that made me order a new lip seal - might as well sort of thing - while I am in there.
What I now realise is that most people are replacing the old aluminium sleeve and the lip seal at the same time - but we have the plastic sleeve fitted so I just ordered the new lip seal.
I am not a 'weak' guy so the fact that I just could not get the b2 piston and the new seal to fit each other with all my pressure led me to ask the question.
I now am convinced that the seal we have installed is not up to scratch and will try and track down the older version of the seal from somewhere - unlike Mercedes it seems that the part number hasnt changed over the years - usually it says 'has been superceded by' when there is an improvement to a part. But as the new one and the old one are definitely different I know that something has changed over the time since this vehicle was made.
The 722.3xx trannys were used in so many Mercs and Porsches that I am sure we have at least structurally the same parts ... and your input is valuable in directing me to my next move - find the old version of the seal OR buy a new version of the piston. (this piston we have has the full teflon edge around the large piston disc not the older version with the teflon inset)
Thanks for your input
Regards
Mark

HI BWhitmore
Thanks for the info - I will email him and ask my question.
Shame we arent 1000 miles further north - we could just pop over and instead of trying to repair in a field have his guys do it for us
Thanks
Mark

I have only limited knowledge of the transmissions. Others have gone further into them.
However, I have not read of anyone having your particular issue with the seal. So I will have to wait to see what solves the issue.

As a Diesel Mechanic for 18 Years I seen parts places send the wrong parts that looked similar to the correct part. It does not happen often but it happens. Of course there is no way for me to tell that is so.
I have also received correct parts that apparently got passed quality control and did not fit.

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84 300D, 82 Volvo 244Gl Diesel