oil level Going up in transmission

Discolored also? Main seal failure. Both gears? Failing at the same time would be a bit odd. Maybe it's been going on for a while.

Detroit and Allison clutch/gear?
Your engine oil is going down also.
There is a seal between the front of the wet clutch and crankshaft end that is failing.

TD or ZF clutch/gear? Review your level checking procedure.

Still not; Send some oil to a lab quickly for testing. Looking for water or coolant.

My first suspicion would be your gear oil cooler. You may be getting water into the oil via a failed tube or similar issue in the cooler.

Oil would be milky. May take while for engine oil to affect the gear oil color

I assume you're checking the gear oil with the engines running. Without engines running the level could show way up on the stick above the full marks.