Took the top part of the cap apart from the rest of it...due to the childproof design.
Drilled two undersized holes in the cap...one for the tire valve and one for a tube that runs down into the bottom of the jug.
These need to be undersized by about 1/16" or maybe a little more to be sure you have LESS air leakage. They also need to miss the top part of the jug that the cap goes on...there is not a lot of room.
I used bearing grease to put the tire valve in...using a valve tool to pull it thru. And put some oil or grease on the tube before inserting.
The exit hose is clear vinyl...and the gadget on the end is from a manual gear oil pump that quit working....holds the hose in the trans.
Tested this using some old ATF...works pretty well...but the flow will be fairly slow.
Be sure and watch that the pressure in the jug doesn't get too high...or guess what...stinky gear oil all over the place. The fittings will continually lose some air, but you should see enough pressure to push the oil out. Just keep on top of it because if you DON'T have air leaks...the jug sure won't handle 100 PSI.
You do need a 12V air compressor...but I already carry one anyway...they don't cost a lot and last a long time...IF you don't try and run them in the rain.
You could also use a portable air tank.
Final note: I used this jug to fill a trans with 90W140 gear oil...and the processs was S L O W. The jug handled the pressure OK though.
Have now replaced the center tube with some 3/8" OD soft copper tubing which has about 4Xs the cross-section of the original tube.
Also am using only the large clear vinyl tubing...not the end piece...allows more flow and the tubing will still stay in the opening if it is wedged in there some.
Found that it still took 12 mins or so to get 1 gallon into the tranny....80W90. Allows some time to think about the meaning of life.
I use a small 12V air pump that has a switch on it in order to regulate the air flow. Due to the inevitable leakage around the tube and so forth...you will loose some pressure...but I keep an eye on the jug and if it looks to be expanding a bit too much I shut it down for a while.
DO NOT just throw a lot of high pressure air at the jug...you might not like the result?[/b]
Just refilled transaxle and rear diff with full 75W90 synth...and found that this refill jug still works very well. I had doubts about getting the 1 oz per qt of Tufoil additive in....but though it was thick...it went in real well when put IN the jug with the gear oil.. You can see the oil inside the jug pretty well...and the bottom of the NEW copper pickup tube (larger diameter) can be raised or lowered so that when you are near the end of what you are putting in...you can lower the pickup tube right down onto a "corner" of the bottom of the jug and get it all out except for a few tablespoons. This works IF you have a couple of small Vs cut in the end of the pickup tube so it doesn't get blocked by the bottom of the jug.
* Still using the same jug after 3-4 uses....looks a bit "expanded"...but no splits and it doesn't leak
* right click to see pics?
Where to CHECK...DRAIN...FILL!
Drain using ALL 3 drain plugs...CLEAN them....reinstall and tighten them...except for the rear one which needs to be left out 7-8 turns. I refill using the front diff plug and with the front of the car on ramps...goes in quicker. Put in the 4.1 quarts... or until it runs out of the hole (overfull)...install the diff fill plug...tighten up the rear drain plug. You're done.

DON'T get your finger stuck in the dike? This means that if you try to use your finger to check the oil level IT CAN GET STUCK....then you will be in dire straights...stuck under your car with your finger swelling...and the rescue guys trying to figure out how to get you loose.
NOTE: Still using this and the TOTAL DRAIN and REFILL METHOD. If in doubt...drain it and add 4.1 quarts. Takes 20 mins...costs are negligible if you use regular gear oil...you get rid of particulates. Clean the drain plugs of fines.
FURTHER NOTE: All proceeds from licensing fees from the TAKZA GEAR OIL REFILLING DEVICE are being donated to a foundation whose sole purpose is to discover the underlying genetic basis for conservatism. Save the chilluns.