I used old rattle can paint tops to catch the oil. Would crack fill plug to let it flow, then snug up the fill plug in to swap out the containers. Worked like a charm, oil pretty much stops flowing when the fill plug is snug.
When I changed the gear box oil I used duct tape to hold a quart size zip-lock bag under the bottom hole. It worked perfect. Not a drop of oil went to the deck or the belt. The filling however was not so smooth. I spilled a fair about after my perfect performance on the draining. My ego did suffer on that.
I'd like to add to this thread by sharing my own experience of changing the gearbox mower oil.
Kubota GR2120 owner manual recommends Kubota UDT transmission fluid to fill it and it is presumably what was put in at the factory. Now, I noticed while using the mower that there was no apparent leak but that the whole area around the mower gearbox appeared kind of oily and that dirt and debris would stick to that area. Whend I emptied the gearbox to change oil at 50 hours, I gathered only about 80 to 100 ml of used oil out of 150 ml that was originally put in. When I contacted my dealership about it, I was told that regular transmission fluid is not suited for this small gearbox, because it expands with heat and tends to leak in the form a a thin mist of oil. They sold me a replacement synthetic oil that is supposed to fare better: cost is 50$CAN for 500 ml (about half a pint). I have yet to receive it and fill the gearbox with it. So, I plan to post an update whenever I gather relevant facts about this situation.
I just received the small bottle of oil: it's a Kubota product, part #70060-03865. No specification on uses or viscosity on the label. Providers on the web simply describe it as "Synthetic gear oil".
Just changed the Gearbox oil of the RCK48GR mower that fits the GR2120. The easy way to go for me was to remove the big fill plug. Pull the deck upright while my wife was holding a small can down the lip of the fill hole. The oil quickly drained, without spilling a drop. Put the deck down and pull it up on its other end, the fill plug being now on top: my wife then fill it up with a pre-measured cup (150ml) of replacement oil and lightly srew in the plug. Put the deck down, secured the plug. Not a drop spilled.
