I have had 3 dodge 1500 trucks the first one a 02 4x4 I did a flush at 85 k, next day it wouldnt shift into 1st gear, somthing about a soliniod and govener $450 later all was well. my 08 4x4 I had a filter change done at 18k just cause, no problems ever out of that trans and I had superchips with the trans tune, that truck ran great. I now have a 11 and plan on a filter change at the normal 30k time frame. Lost story short my experiance is that it doesnt matter either way except if you have miles on your vehicle when you get new fluid in there it will loosen up debris from your tranny cooler and it will take out your trans, change fluid early and often