I have a 98 Dakota with the 42 RE transmission. When I come to a stop it will only down shift into 2nd. it will not go into first. The truck set for almost a year. I do have a sevice eng light on so I had it checked out and they said it could be one of several things. I would like to know if anyone else has had this problem. The trans is good they feel it is electrcal. possible solinoid, or govnor.

 

You should be able to pull the transmission codes. Here's a site with instructions and code explanations:

http://www.fseg.net/Mopar/42re.pdf