It might be conicidental, but recentally I put my 04 150 in 4 low just to make sure it engages. The light came on, I was satisfied with not even moving, and disengaged it. Light went off. I couple days later I started to notice a "moaning" noise during 2 wheel drive driving. It is just about at regaular intervals of about 2 seconds. When I switch to 4 high while driving, I feel the engagement and then the noise disappears. Is this noise coming from the transfer case? One more thing, I think I have a leak somewhere. What color is transfer case fluid?

 

redish pink

 

FYI The problem was two barrings(sp?) and two 4 wheel drive actuators needed to be replaced. Thank God for the extended warranty. Would have costed $800 bucks.