Hello I will help you with your question,
For your 2001 Ranger if you had 2WD and a manual transmission you could tow as is, the automatic required a driveline disconnect to keep the transmission from being driven by the rear wheels.
The 4WD is a lot more costly, you would need disconnects for both the front and rear driveshafts.
One site that helps with this information is below
Another is found here (Click)
Let me know what I can do to help you with this
The limits are imposed by Ford legal to limit their liability. You want to be sure the transmission stays lubricated by operating the truck for at least five minutes each day but you do understand that you will need to install driveline disconnects on BOTH the front and rear drive shafts for your four wheel drive truck?