whiny P38 & Another Question

My 4.0 seems to be getting whiny in the transfer case... I can't remember
how it sounded when I got it..
Serious?
What's the worst this may indicate?

Also, I just found that the manual says to NOT leave the Cruise control on
all the time- whoops, I've just left it on for, let me see now- yes, 2
YEARS. It still works- but have I hurt anything?

Thanks chaps (& chappettes)