Chirping noise coming from transmission?

I recently bought a 2004 Ford Explorer 2wd Eddie Bauer with the 4.6L v8. It has about 62K miles on it. When driving on the street at a steady speed, it makes a quick chirping noise. It doesn't do it when shifting, just when driving. It also doesn't do this when sitting idle. It does have some shifting issues, like occassionally slipping or shifting hard, mainly from 2nd to 3rd. The occassional chirp is kind of irritating.