i dont know how 97 sr5 5spd 4wd works but this is how an 01 sr5 auto's 4wd works...
when youre in 2wd, the button is out, and the shifter is placed in H. When you want 4wd to be on, you push the button in. the lights will begin to blink. you must be in motion for it to actually engage. once you get to a decent roll, youll hear a "pop"/"clunk!" and the lights will stay on. this means 4wd H is on. to go into low, come to a stop, shift your auto tranny into N, then shift the 4wd shifter all the way forward. dont do this too quick or youll hear the crunch!
the general rules are:
-dont shift into 4wd above 55mph or so, it will not engage
-if you want to turn it on while driving (say at 25 or 30 mph), it wont engage if you are accelerating (so let off the pedal while in motion and it should engage right away -- mine does)
- to disengage you must also be in motion.