[titanjbc]

Please, please read the section in the Owner's Manual on towing. Although the marketing says that the truck can tow 9500#, there's a few "buts" in there. You have to take into consideration the weight of the passengers, fuel, any equipment in the bed, etc. As said here, you MUST use a WD hitch, which transfers weight to the front axle of the Titan and axles of the trailer.

I tow a 6000# trailer and I was right at the GVWR of the truck (I weighed my rig at the truck scales).

Also, what kind of trailer is it? Boat, RV, other? How long is it? I use a WD and sway control system for my 24' trailer. If your trailer is longer (say 28'+), that could be the reason for fishtailing. The other is that there's not enough weight forward of the trailer.