How do I find out what transmission my 2003 Dodge Durango has?

I'm wanting to do a transmission service and there are 4 transmission options to choose from. It is a 2wd with 4.7 lt engine. Thanks for your help.|||You have a 45RFE trans, common to most 4.7`s.|||the company will know by the vin number.|||Check your owner's manual.