Transmission clutch k-1 totally burnt!? What causes it? - PeachParts Mercedes-Benz Forum

Victor300E · #1 08-14-2007, 05:34 PM

Hi guys,

I bought a broken tranny 722.366 for my 92 500sel and rebuilding it. Seller didn't know much about it since it was a core return. Tranny looks to be serviced before becauseit has fresh paint. Now the funny part: all clutches are fine exept for k1. It is tatally burnt and even steel plates cannot be reused since they have grooves in them. Clutches have no lining at all and all deformed. I couldn'd take k1 drum off at first because they were jamming.
Question: what is causing k1 clutches to be burnt like that? I don,t want to put new set and burn them again

Please help!!!

Thank you

mbdoc · #2 08-15-2007, 08:22 AM

Most likely the 2 teflon seals on the "snout" of the front pump housing assembly.

There is a non-replaceable o-ring INSIDE the k-1 clutch drum.. I would air check that drum to make sure it doesn't leak.

Victor300E · #3 08-15-2007, 05:40 PM

Thanks again M.B.Doc,

I checked 2 teflon rings on front pump assembly. They look new. No caracks or grooves or any other sign of damage. I also disassembled k1 drum and found 1 seal on the piston itself that also looked new. I cannot find any other openings that I can blow into a drum to check if its leaking. Drum looks good. There is lots of residue inside the pan and inside the drum. It's greyish-silverish in color. Looks like oil or something. There is no residue in k2 clutch drum though. K1 however was all filled up with it. I assume it is burnt friction disks lining mixed with transmission fluid. I was thinking if residue blocked the piston and kept clutches engaged thus burnt them. Or is there a way that valve body have aproblem and keeps clutches engaged. I will post some pictures tonight hopefully.
I'm stuck here with tranny in peices and don't know what to do to it. It would be pointless to rebuild it and have k1 burnt again.

Any suggestions?
Thanks.

Victor300E · #4 08-22-2007, 09:40 AM

Here are pictures of some damaged and good parts

Victor300E · #5 08-22-2007, 09:45 AM

here are more pictures. I'm suspecting a seal that is on k1 piston and seals piston to its body. If I were to check it for leaks it would definatelly fail. It does not seal good but it was replaced when tranny was rebuild. Maybe the piston itself of picton body are deformed? What do you think guys?

dpetryk · #6 08-22-2007, 09:58 AM

As mentioned earlier there is a large O ring at the base of the K1 drum. The only way to replace it is to drill out a few rivets. Replace the O ring and then I tap and countersink the holes and replace the rivets with flat head screws and thread lock. If you don't replace this seal you may never get the proper pressure for the piston to pump up properly and the thing will slip and eat the friction material again.

Victor300E · #7 08-22-2007, 03:00 PM

I'm cofused now. Is k1 drum in front of tranny right behind primary pump, or behind closer to rear wheels? If it is in front then there are no rivets in it. There are rivets in rear drum and I assume it would be k2. Now if k2 is leaking pressure will it effect k1 drum pressure? Theoretically it would but will k2 clutches get burned as well?

Thanks