I have been looking at dodge cummins 1999-2002. I am wondering what automatic transmissions they used, how many gears in them, and if they are durable?

 

They have the 47re. They are durable as long as the truck is within 60 or so hp above stock and they arn't abused, after that it is a guessing game. Some will last longer than others. Best thing to do is make sure clutches are good and go ahead and put a valvebody and torque converter in it and youll be good to go if your planning on adding some hp to the mix.