I had some people PM about how to do the removal so I thought I would post some of my response with a picture incase anyone else is thinking about tackling this job. Its actually REALLY easy to drop the tank. I was surprised!
There is literally only 4 mounting bolts that hold the whole assembly up. I would recommend using a jack as I did underneath the tank if you know you had a bunch of DEF in it.
First, put the jack under it so its barely touching it. Remove the 3 tiny screws that hold the filler neck and vent assembly behind the fuel door.
Next, remove the four bolts that mount the skid plate/DEF assembly up underneath (see attached picture for mounting locations underneath the truck). If you are removing any bolts that have a nut on them, you are removing the wrong ones. These all have the clip on speed nuts mounted to the crossmembers underneath and one on the framerail.
Once you have it free, slowly lower the jack down. You will see one big electrical connector up above that you will have to disconnect after you lower it 6 inches or so and must do this before you can drop it any further.
Keep lowering it down while keeping an eye on the filler neck assembly. You want to make sure that when its lowered more you can push the filler neck over the frame rail to the side where the DEF tank is. Then it will be completely free to keep lower almost all the way to the ground.
There is only one more thing that you will need to keep on eye on as you are lowering. The tube and electrical connector that supply the DEF from the tank to the injector. You will see the tube mounted up underneath with some christmas trees and should remove those before lowering to far. As you lower it down (which I was able to take it almost to the ground), you will see there is a quick connect tube that has an electrical connector on it. Disconnect the two from the DEF pump.
And there you have it. Its completely free to lower to the ground and slide out from under the truck!
-Nathan
