I have a Case 621 wheel loader JAK0021043 S/N. The left rear planetary keeps going down. There seems to be no external leak. I was thinking there must be a seal to keep the oil from traveling to the drive axle. I looked at several parts diagrams but I found no such seal. There only seems to be the seal that keeps oil from leaking to atmosphere. Am I wrong? Does the oil travel back and forth from the drive axle to the planetary, and if so why is there a plug to check the planetary oil level?
The planetary cover plug is turned to the 9 or 3 o'clock to top it off and there is no seal in the tube that i recall, The center holds around 12 qts, and the planetary 3 qts each side i seem to think. Most lube will stay contained in the planetary but could flow some to the bowl parked on a hill sideways, tire pressure ( had a flat lately) by a worn thrust washer maybe. It all vents together also. I would check my fluid in the center, clean the breather, refill both hubs (plugs turned for correct level) and watch them inside rims and seal area really well while keeping a check on the lube in that one side.
Not sure about case axles, but most Clark axles had a channel in the casting that would catch splash oil from the diff and send it to the plantetaries to replace oil that was splashed from them into the axle housing and back to the diff housing. If that channel was plugged, the planetary on that side would starve for oil while running and gravity feed back when the machine was parked as long as the diff level was higher then the tubes to the planetaries and the machine was parked on level ground.