722.3 - B2 Piston Case Seal - Part # ? - PeachParts Mercedes-Benz Forum

Richard Howard · #1 04-22-2010, 01:31 PM

I've done a lot of searching, both here in the forum and on the internet, trying to find a part number for the black rubber/neoprene lip seal that the polished aluminum small end of the B2 piston fits into in the 722.3 transmission.

This is the lip seal that fits tightly into the transmission case.

Does anyone have a MB part number for this seal? Is there any newer part available that supercedes this black neoprene lip seal?

The transmission # is 126 2702801 722.303 02 409978, in an 84 300SD with VIN WDBCB20A6EA008924.

Thanks very much for any information.

Mazootpusher · #2 04-22-2010, 05:29 PM

The only part #'s I found for the piston lip seal ring are # 1242720255 and Genuine Mercedes # 124.272.02.55. you should verify with the dealer!

Richard Howard · #3 04-22-2010, 06:57 PM

Thanks. I'll try this number at the MB dealer; they've been great with providing parts that I haven't found at FastLane, even though Phil Reinhardt has always served with 110% effort and results for parts I've bought there. The dealer was, however, stumped with this request for this B2 piston case seal. It doesn't even appear in any of their pictorials for the 722.3 trans. that they uploaded from their system.

Mazootpusher · #4 04-22-2010, 10:01 PM

I also found this for a 722.353 transmission b2 piston rubber seal part # 006-997-73-47-M104 .it may fit the 722.303 ??
see attached picture.

Diesel911 · #5 04-22-2010, 10:40 PM

Does the below Bushing go into the Trans first and then the Rubber Seal goes on top of it?

Richard Howard · #6 04-23-2010, 08:20 AM

Diesel911, I've wondered about your question also. I don't think the bore is deep enough to accept both the teflon/nylon bushing, with the lip seal against it to center it and keep it in place. I suspect there is some other part that's used to keep the bushing located correctly and to prevent it from moving when the piston moves. This is an obscure point that maybe only those in the Mercedes transmission rebuilding business have an understanding of. If I can get the lip seal from MB I'll probably just go with that for a fix with the new B2 piston I have.

Diesel911 · #7 04-23-2010, 11:41 AM

Quote:

Originally Posted by Richard Howard

Diesel911, I've wondered about your question also. I don't think the bore is deep enough to accept both the teflon/nylon bushing, with the lip seal against it to center it and keep it in place. I suspect there is some other part that's used to keep the bushing located correctly and to prevent it from moving when the piston moves. This is an obscure point that maybe only those in the Mercedes transmission rebuilding business have an understanding of. If I can get the lip seal from MB I'll probably just go with that for a fix with the new B2 piston I have.

From what I reacall from this forum the Nylon Bushing replaces a Steel Sleeve.

Richard Howard · #8 04-23-2010, 09:08 PM

Diesel911 and interested others: After never having seen any pictures or diagrams of how the B2 piston, the lip seal, and the bushing relate, I just tonight realized the relationship between the new plastic bushing and the lip seal mentioned in the posts above. I then proceeded to get the old steel bushing out of the 722.3 case so the new plastic bushing can be put in its place. Here's how I did it:

I used one arm (4" long) from a small three arm puller, bolted it to the handle end of a 10" long Craftsman 3/8" drive swing handle, using the hole in the handle end that's intended to fit on a supporting pin on a storage pegboard.

I then hooked the narrowest end of the 4" puller arm onto the inner edge of the old steel bushing, placed the swing handle against the outer surface of the B2 bore (just outboard of where the cover and retaining ring fit), and then hit the other end of the swing handle several times with the heel of my right hand. It took only several repositionings of the puller arm's "tooth" around the steel bushing before the bushing came out of the bore.

The new plastic bushing (126 277 08 50) goes into the bore small end first, with the thin small shoulder outside. 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.

It was again really amazing just how quickly insight and understanding can appear after pondering a problem for a while...

Diesel911 · #9 04-23-2010, 10:01 PM

Thanks for the info.
But, another question. What way did the Old Lip Seal Face; did the Lip also face away from the Band/Pin?

Mazootpusher · #10 04-24-2010, 10:19 AM

I must have misunderstood the original question! you were referring to the "O_RING SEAL" that fits in the lip inside the bore.

Richard Howard · #11 04-24-2010, 07:54 PM

The old lip seal had its lip facing outwards towards the cover, away from the band and pin. I assumed it was the original and was put in correctly. With the lip facing away from the band, when a shift from 3rd to 4th gear was to be made, fluid under pressure would then enter the bore area between the B2 piston and the piston-to-case lip seal, moving the piston back towards the cover, to unclamp the band as required to allow the shift to occur.

Note: post was edited per request of the originator to reflect what is believed to be more accurate information.

Diesel911 · #12 04-24-2010, 10:34 PM

Quote:

Originally Posted by Richard Howard

The old lip seal had its lip facing outwards towards the cover, away from the band and pin. I assumed it was the original and was put in correctly. With the lip facing away from the band, trans fluid under pump pressure would move the piston towards the band to clamp the band when a forward gear was selected. Fluid under pressure would also tend to force the lip against the polished aluminum surface surrounding the apply pin's pocket, preventing or minimizing any leakage of fluid from the piston's bore to make sure the band was clamped as tightly as possible.

Thanks.

whunter · #13 04-25-2010, 11:46 AM

Quote:

Originally Posted by Richard Howard

I've done a lot of searching, both here in the forum and on the internet, trying to find a part number for the black rubber/neoprene lip seal that the polished aluminum small end of the B2 piston fits into in the 722.3 transmission.

This is the lip seal that fits tightly into the transmission case.

Does anyone have a MB part number for this seal? Is there any newer part available that supercedes this black neoprene lip seal?

The transmission # is 126 2702801 722.303 02 409978, in an 84 300SD with VIN WDBCB20A6EA008924.

Thanks very much for any information.

Picture/data attached.

Have a great day.