Are you changing out the gear oil, or just topping it off?
The simplest way I've found to get it in there is using the 1 quart bottle
of gear oil with the pointy cap. Put the little funnel in the fill hole
angled down, and squeeze. Tilt it back up, let the bottle return to shape,
repeat until topped off. I bought a gallon of gear oil and filled the quart
bottle up again to finish the job, and kept the small bottle for when I need
it again. Way faster than a funnel/hose.

Cya,
Robert