about my 4wd explorer

hi,
 I have a 97 eddie baure explorer and when i put it in 4wd it makes weird noises when i turn the wheel to the left or right. i have never turn my 4wd on asphault or concrete. what is that noise and where is it coming from and how can it be fixed??? another thing is that my 4 wheel low does not work. when i put it in neutral i will turn it to 4 wheel low and then it will click like it wants to go into 4 low but it does not. when it clicks it clicks several times like it is going into 4 low nut its not. i think it is the solenoid but dont know. is it the solenoid or is it somthin else? how would that be fixed? are both of these problems going to be expensive to fix???

There is an electric motor on the back of the transfer case that switches it into Low, High, etc. It could be slightly shot.