Anyone know what will happen if I press this ECT power button?? Will it give me 50/50 power distribution or will that make it 70/30, or 40/60, etc.?? Thanks!!

its like driving a standard, the shift up to the next gear is at a higher rpm than normal. If you want to play and drive a little more aggresive in a RAV4. Press the button and then find a good stretch of road, floor it and watch your tachometer each time the trani shifts. You should notice a good difference.

It's mainly used for towing purposes. It keeps it in gear for a tad longer before switching gears. Gives the car a little more umph when needed.

So the ECT does not change the power ratio at all then? What is the current power ratio on my 2000 Rav4? Is it 70% in the front and 30% in the rear, or is it 50/50 at all times, or is it 50% front wheel drive and kicks in the other 50% in the rear when its needed?

No it does not. Like I stated before, it just changes the shift points in the tranny when driving; holds it in gear a tad longer before shifting up to the next gear, it does nothing to the power ratio.

This explanation is intended as a real basic overview of your 4WD.

First it is not a 4x4, which would allow you to select 4High, 4Low, 4Lock and Neutral, all of this is accomplished through a Transfer/case. You own a 4WD, your Rav4 uses the same principles , without input from you, all electronic. Place the shifter in D and go, all wheels have the potential of having power sent to them. You have Vehicle Speed Sensors (VSS) at ea wheel sending speed info to the Computer. The computer decides where to send power. On my RAV I have an additional button that sends power to all wheels until approx 50kph. Then it shuts off and your justa 4WD again. Vision a parking lot with real deep snow, press the button and drive right through.
To re-cap. 4WD is not the same as 4x4. Place your RAV in D and go, the computer will detect the tires that are spinning and those that aren't and with the info from the VSS a message from the computer decides. If you have a Scan tool that can read VSS, you can, while driving, see the readouts of ea wheel as it spins. Then you can do the math ref percentages