actuator

1997 Chevy K1500 5.7 with a 4L60E trans. my four wheel drive acted up today i am doubting if it goes into four wheel drive (havent jacked it up yet) but the light on the dash just blinks i had a buddy put it in 4X4 while i watched the front drive shaft it is turning but this doesnt mean the front differential is locked in...also i noticed the past couple of times when i wanted four wheel drive i would have to go to neutral push the button then go to reverse for it to lock in...it wouldnt do it any other way what would cause this is it just the actuator on the front differential giving me all this trouble ??? everything i have read leads me to the actuator but the reverse thing threw me for a loop any help is greatly appreciated

well i bought an actuator didnt fix the problem i dont know what it could be now...when the 4x4 button is pushed the wire going to the actuator gets power the actuator gets hot the plunger extends...what else could it be ?? what does the plunger push on inside the fron end a fork ??