Sometime during this gearbox's life it was repaired and resealed with ineffective sealant that allowed severe leakage. When I disassembled the unit I discovered that this was the least of it's problems. First and fourth gear were both cooked; the spray bar was completely clogged and the pump check valve was missing- yes, missing. I replaced the first gear set which included the main shaft, unclogged the spray bar and rebuilt the box, replacing necessary components and, of course, installing a missing check valve.