i push the button for 4 wheel and the light turns on but does not engage 4 wheel. was working fine till now. never a problem before this. any ideas?

put it in 4wd and see if you can hear the tcase making a hiss-then-clunk sound, or put it it in 4wd and try to turn the front driveshaft. If you can't turn the front shaft then your front actuator is either broken or has a loose/bad connection.

it was the pump rub in the tranfer case. it had rubbed a hole in the case at only 144000 miles and it ran dry. and no this one wasn't my truck it was my friends