For a while I have been trying to narrow down the cause of low trans/steering clutch oil pressure on my D6c 10K. (discussed in a previous thread) I think I've finally traced it down to the steering clutches, which is usually the culprit. I spent some time making sure it wasn't something else because the steering clutch seals were redone not long ago and didn't want to tear them down until I was sure. I ended up pulling the steering clutch covers and made up a steel plate to hold the oil pressure tube in place so I could run the tractor and view the clutches. Oil is leaking around the rotary seal between the bevel gear bearing cage and the steering clutch hub. (at low rpm and cold they leak about like pouring soda out of a pop bottle) I pulled the steering clutches but haven't pulled the hubs off the bevel gear shaft yet (will have to rent a puller). I got all new seals from Cat and was comparing the piston seals to the old ones. The old piston seals have about 1/8" end gap (split seal) and the new ones aren't much better. Can't imagine they would work very well. I would like to have seen the gap good and snug when I put the seals into the bores. The rotary seals (that I don't have apart yet) are made a little different in that they are a split seal but the ends are half thickness and overlap each other. This looks like it would work better, but that's where I'm seeing my bad leak. What do you normally see for end gaps on seals like these? Was hoping Cat seals would be better. Has anyone checked steering clutch leakage by pulling the covers like I did?.....If so how much leakage did you see?
Not sure if I have talked about this to you. With the top off pry on the clutch flange and look for shaft end play. I suspect the bevel gear bearings have failed and allowed the flange seals to blow out. Later Bob
Bob, When I worked on it last time I replaced the bevel gear bearings....less than 500 hrs ago but I will check to be sure the preload is still good. After replacing the seals last time I didn't get any improvement in clutch drag. The one thing I can't remember for sure is if I replaced the bearing holders. I know I took the clutch parts to a local shop to get their advice, but I'm not sure if I got new ones. There was a small amount of seal wear in the inside of the bore. Can't find any old parts laying around so I probably didn't. Could be part of the problem. Still baffles me why Cat would leave such a large end gap on the piston seals. That type of seal relies on oil pressure getting under the seal and forcing it outward to seal against the bore. With a large end gap the seal can have a large gap making it harder to build seal pressure. If I could figure out a good way to cut down the thickness on the ring seals I'd be temped to cut them to half thickness and put in two seals so the gaps don't align.
The leakage is not an issue, clutches are spring applied oil released. Leakage on an oil applied clutch is an issue. If you pull the flanges you can repair the bores of the cages with JB weld and sand it smooth. Make sure the release pistons are in the right way or they will blow a seal out and not release the clutches any more. Later Bob
The leakage is what my problem is....not getting enough pressure to the clutches to release them properly, especially at lower rpm's If I block off the steering clutch tubes where they enter the bevel gear case I get pretty good pressure.....unblocked I lose about 100 psi.
Okay maybe it's the flange seals and cages, make sure the release pistons are installed with the outer diameter seals towards the center. Have seen a 977/same setup, with pistons in backwards and they blew the rings out first release. Later Bob