Transmission shift problem
 

Hello, I just got a 1999 2500 diesel. I have had it a week. The last few days I noticed a problem with the transmision. In town it almost skips 2nd alltogether. It shifts to second gear then to third within a couple of seconds.
Then on the highway it jumps in and out of overdrive unless I get on it. Once it gets past 60 mph its ok. Any suggestions?