At what rpms is it running at and on my John Deere 5575 there is a oil pressure valve that you can adjust with shims too increase the oil pressure if needed.
I have a 1996 5575 John Deere skid steer and the gear oil looks milky when I opened the plug between the two tires. I just got the machine a few months ago and I'm trying to learn everything about it also at what RPMs should I be running the machine at when I operate it.