Transmission Speed Shift Lever - Move the lever (1) to one of the four desired travel speeds after pushing neutral button (2). Shifts between any gear speed can be made while machine is moving.
Move transmission speed lever as per shift pattern on the machine.
Speed changes while moving and at full engine speed are possible. However, for operator comfort and maximum service life of power train components, decelerating and/or braking, when changing speeds is recommended.
Neutral Control Button - Push the button (2) in when changing speed ranges. This will disengage the transmission from the driving wheels.
Push the button when all available engine power is desired for the loader hydraulics.
Neutral Button (8) - Push the button in when all available engine power is desired in the loader hydraulics. Push the button in and transmission will disengage from the driving wheels.
Release button to return the transmission to gear it was in previously. Machine is free to roll after button is pushed. Push the brakes to stop machine movement. Neutral button also on transmission speed selector.
These two buttons need to have a complete circuit to work. It can cause the disconnecting of the transmission but, it should come back when you shake either lever or the wires make contact. Not sure if it is your problem, just wanted you to know it could be a problem.
The oil color difference could be from air in the oil, this could mean the suction screen is blocked and is causing the oil to foam. The oil in the tube would be the last to turn foamy.
The oil needs to be drained to remove the screen. It holds a little less than three gallons and a third will likely stay in the convertor.
Drain the oil and clean the screen. Refill with new 30W transmission oil, TDTO is the CAT spec'.
If no problem is found or debris seen in the oil or screen, inspect the wiring from the neutralizer buttons on the shift lever and the loader control lever. I have seen them damaged often and the customer would just twist the wires together to get a circuit until they decided to fix it.
If this does not help we may need to check the shift solenoids. They are on the top of the transmission and the floor plate needs to be removed to access them.
Let me know what you find and we can go from there.