I have a 550h john deere with less than 2000 hrs on the machine. Had the seal between the trans and hyd. pump got pushed in letting the trans oil leak out the breather in the hyd. pump . This is the second time this has happened . First time was at 1600 hrs. had the pump rebuilt and lasted roughly 400 hrs . machine worked fine with no other problems. Any ideas ?
Issue is high case pressure in the transmission pumps pushing oil through the front seal on the hydraulic pump. The motor case drains and both hydrostat pump case drains all tie together and pass through the oil cooler on the way back to tank. So, could be plugged tank breather causing high tank pressure, clogged cooler, malfunctioning cooler bypass valve maybe, high case drain flow from one or all of the drive motors and pumps, restriction in a case drain line somewhere. Sounds like it's getting worse as the new seals only lasted 400 hours this time. Problem is not in the hydraulic pump unless they're using the wrong seals or the shaft/bearings are bad, ruining the seals. Outer seal has to be installed with the lip out, to keep oil in the transmission pumps, I've seen guys put them in backwards out of habit. I would get a charge pressure and case pressure and flow analysis done, see if one particular component is at fault and get Deere to help out on the repair cost, usually if you ask nicely and mention the original failure at low hours, the factory rep will go to bat for you.
An 550H with those hours no way. That dozer was made in 99 to early 2000's. Unless your the original owner. The hydrostatic and hydraulic tanks do not have breathers. I know this sounds odd but true. I do agree with lantraxco on the charge pressure or case pressure. But deere is not going to help on this one. I worked there for 17 yrs. it only had at most 2 year warranty.