Recently the hydraulic motor on my 70D final drive ruptured the seal due to a bearing failure. We pulled the motor off and replaced the seal and bearing. The surface the seal rides on (output shaft) is fine. Went back on the machine within about 20 seconds of working it begins to gush a very large volume of fluid out between the gearcase and the motor. Removing the motor the seal and the mating surface of seal rides on are both fine, this is confirmed by my brothers who are both Red Seal machinist. The oil is only in the cavity between the motor and final drive, no large amount of oil is coming out around the port that goes to the parking brake. I even went so far as to make a couple short hoses so we could spin the motor up sitting on the ground and there is not a drip coming out of the output shaft seal. Video attached. We have made sure the mounting surfaces are perfectly clean yet this thing continues to **** hydraulic fluid out. Gear case is not full to the top of oil, but I'm wondering if the parking brake on this thing could cause enough oil to go into the gear case and sneak by the mechanical seal back around the gear case input shaft. The sheer amount of oil coming out of this thing is far in excess of what I think could get by any leaking seals so I'm thinking the parking pin must be pissing oil into the gear case but I find it odd that it is not filling it up to the top so perhaps it also ruined my Duo cone seal. is it possible to inspect the brake without removing the final drive from the excavator or am I going to have to break the track and walk this thing off? I was hoping to pull the front off the final drive and be able to get the gears out and work on it with basic hand tools as I have a bad wrist and don't think I have the necessary gear to lift the final drive off the machine once loose. for what it is worth here is attached video of the hydraulic motor running with no leak we drilled and tapped the port that applies pressure to the brake and put a bolt in it to do this test. After having this rather simple pump apart there is of damage on the inside I just can't see it losing nearly a liter a minute through what appears to be a perfect seal. So that's why I'm thinking about opening up the gear case to check the parking brake, maybe some debris got in from the bearing failure and jammed it open. Looking for any of the old professionals ideas on this one. This is a fantastic old machine..
If the duo cone seal was bad, there would be oil leaking on to the inside of the track sprocket. Just need to remove the motor to get to the brake piston and piston seals. See screenshot below from Deere’s online parts. https://partscatalog.deere.com/jdrc/sidebyside/equipment/63405/referrer/navigation/pgId/2950 .
Glad I checked. So how does the shaft come out? Seems to walk back and forth an inch. I assume that piston comes out the hole covered by the motor?
Yes ,the brake piston comes out the bore covered by the motor. I don’t believe the shaft has to be removed.
FYI, I edited post #2 by adding, “If the duo cone seal was bad, there would be oil leaking on to the inside of the track sprocket.”
Ok thank you. I have attached a photo. That grey thing has to come out somehow? Any tips, it doesn't seem to move.
Do you have air compressor? Put a bit of air pressure into the brake port
Was just thinking that. Thanks DD!
Bingo. Thanks all. I am glad I checked, was getting ready to pull the gearbox off...