The front axle on my M6040 is vented. Dead center, top of the axle housing. A VERY difficult place to locate. It's a screw in plug with a nipple. Rubber hose attached to the nipple. Hose goes up - connects to a steel pipe - terminates in a 180 bend at the very top of the radiator.
Makes no mention of this in my Owners Manual. Had to put a small filter on the end of the steel pipe. Mud daubers like to fill the end with they eggs/goo.
/ Pressure build up on front axle of a 4410 John Deere compact tractor
I know this is an old thread but hopefully it helps someone.
I just drilled a 1/16th holeat the very end of the existing T shaped indentation in the yellow plastic dipstick cap. I stuffed some filter material in that same indentation to prevent any debris. Works well.. I am also using 80W/90 geear oll.