Here in NY, the CDL rules are as follows: 1. 26000 gvwr you need a cdl 2. 10,000 lbs trailer you need a CDL If your truck has a gvwr of 25,999 and your trailer has a gvwr of 9,999 you don't need a cdl. The important numbers are 26000 and 10000, don't worry about the combined weight. So if the f450 has a gvwr of 15,000, but trailer is 10,000 or more you would need a cdl for that combo.