Transmission Front Seal Replacement - PeachParts Mercedes-Benz Forum

New2MB · #1 10-04-2010, 09:08 AM

I've searched around quite a bit and not coming up with the information I need so...

I've got the transmission out of my '87 SDL and I would like to replace the input shaft seal.

When I ordered the front seal it came with a large o-ring, a front pump gasket, and two nylon snap-rings.

So it seems that I am to pull the pump in order to R&R the input shaft seal.
Is that correct?

sixto · #2 10-04-2010, 12:42 PM

Yes.

Sixto
87 300D

biopete · #3 10-04-2010, 02:28 PM

What was your symptoms of the leak? A lot of fluid coming from the torque converter bell housing?

New2MB · #4 10-04-2010, 06:13 PM

Quote:

Originally Posted by sixto

Yes.

Sixto
87 300D

Have you done it or do you know of a thread where someone has?

It seems somewhat common but I can't seem to find any reports on the actual steps.

New2MB · #5 10-04-2010, 06:15 PM

Quote:

Originally Posted by biopete

What was your symptoms of the leak? A lot of fluid coming from the torque converter bell housing?

I was told by the PO that it needed one. When I got the transmission out I could see a small "river" coming out of the bottom of the front seal so the diagnosis appears to be correct.

sixto · #6 10-04-2010, 07:11 PM

Quote:

Originally Posted by New2MB

Have you done it or do you know of a thread where someone has?

It seems somewhat common but I can't seem to find any reports on the actual steps.

I hope you have a good internet connection -

http://avtopedia.ru/akpp/722-3%20722-4.pdf

Sixto
87 300D

New2MB · #7 10-04-2010, 07:52 PM

Wow, thank you for that, looks like everything I need.

Any idea if I can get through it without the installation fixture and installation sleeve?

Doesn't look good.

loepke72 · #8 10-04-2010, 09:44 PM

I'm guessing this is the 722.3 transmission. Usually the large O-ring that goes around the pump body turns rock hard and leaks. Fortunately if that's all that's wrong the pump can be removed from the front of the transmission. There are two threaded holes 180° apart that have nothing in them, these are used with bolts so that the pump can be removed easier by pulling on the bolts (after the pump bolts have been removed, of course). If disassembling the pump to clean it, make sure to pack grease or vaseline in the pump gears or they won't pump trans fluid. The converter seal is installed flush with the pump; don't drive it in further.

New2MB · #9 10-04-2010, 10:20 PM

Quote:

Originally Posted by loepke72

I'm guessing this is the 722.3 transmission. Usually the large O-ring that goes around the pump body turns rock hard and leaks. Fortunately if that's all that's wrong the pump can be removed from the front of the transmission. There are two threaded holes 180° apart that have nothing in them, these are used with bolts so that the pump can be removed easier by pulling on the bolts (after the pump bolts have been removed, of course). If disassembling the pump to clean it, make sure to pack grease or vaseline in the pump gears or they won't pump trans fluid. The converter seal is installed flush with the pump; don't drive it in further.

Yes, the 722.3.

I have the o-ring replacement so I am planning on doing that but it appeared to me that the seal at the very front of the transmission, that seals around the shaft that goes into the torque converter, is leaking.

From my observations it appears that I can pull the front seal (is that what you are calling the converter seal?) without disassembling or even removing the pump.

Is that correct?

loepke72 · #10 10-05-2010, 07:41 AM

Yes, the converter seal can be replaced without removing the pump itself. Usually that seal is not the cause of the leak, though, at least in my experience. The large O-ring, however, the pump has to come out and be disassembled to do that. Also, I recommend using Loctite or a similar sealant on the pump bolt threads. As far as the installation sleeve (or seal protector as they are sometimes called), I did this without the special tool. I installed the retaining ring for the piston return spring in its groove which allowed the inner piston seal to not catch in that groove. The retaining ring is round, so the seal should carefully pass over it. The outer seal has to be carefully worked into place, preferably with a dull plastic tool if one is available. Also, the service manual states the pump to case gasket is reusable several times if it isn't damaged.

New2MB · #11 10-05-2010, 08:31 AM

It sounds like I should do the o-ring regardless of where I think the leak is coming from.

The outer seal you are referring to is the converter seal or is this something different?

jonbobshinigin · #12 10-05-2010, 09:23 AM

Check it out:

http://w124-zone.com/index.php?s=transmission

loepke72 · #13 10-05-2010, 09:23 AM

The outer seal is just a big O-ring that's the diameter of the pump. Chances are you'll have to chip it out due to it being hardened. Then, you might as well put in reverse clutch piston seals since you'll have that out anyway.

New2MB · #14 10-05-2010, 01:55 PM

Thank you very much for your help, I would never figured that out!

Everything went well but I did leave one tiny scratch when re-installing the snap-ring, should I try to remedy that while I've got it apart?