The plug is removed from below and the tube is inserted into the hole. Using a funnel in the top of the tube, pour transmission oil until it can be seen running out around the tube. Replace the plug and keep the tube for future filling. Clean up the mess so the Eco-cops don't arrest you!
This enables you to add transmission oil without having to remove the tunnel cover.
And this from Mgordon736@aol.com
Another easy solution is to go to a marine supply store and buy a pump that is designed for filling the lower unit of outboard motors. It comes with a plastic hand pump that fits into a quart bottle of outboard motor lower unit oil, plastic tubing to connect the pump to the lower unit, and an antiretraction valve (keeps the oil from flowing back into the bottle between strokes on the pump).
Pour out the outboard motor oil and fill the bottle with transmission oil. From under the car, remove the fill plug, put the tubing with the antiretraction valve into the hole and start pumping. When the oil starts to leak out, stop and replace the fill plug. You should lose less than a teaspoon (5 ml. in England) of oil.