I have a 99 Durango that wont shift into 3rd gear until the car is totally warm. Any ideas what is wrong?

The car has to be driven atleast 15 miles or so until it will shift into 3rd on its own. You can rev the engine up to 4000 rpm's in 2nd gear and then take your foot off the gas, and the transmission will skip 3rd and go into overdrive. Otherwise when you first drive it and it is time to shift into 3rd, it seems like the transmission disengages and the engine just revs up like the transmission is slipping. Can anyone give me any ideas of what the problem could be? I have checked the transmission fluid and the color is not bright red, but it also doesn't have a bad smell. And after a 10 mile drive, the transmission fluid is barely warm.