Is 4k the dry weight or the actual loaded-on-the-scale weight? If it's a dry weight, the scale weight will likely be at or more than 5000 lbs, loaded, wet, with all the amenities.... Water (7lbs a gallon), propane tank(s), battery, fridge, stove, furnace, air conditioner, awning, luggage, pots and pans, bedding, toiletries, etc, etc, etc all add up way faster than you can imagine.
Oh, and 1000 lbs on the rear axle is likely going to put it well over the GAWR for the truck... I'm pretty confident of that one. Take the truck to a CAT scale at almost any truck stop, and for $8.50, you'll know exactly what it weighs and how much extra axle capacity is available.... Subtract 100 lbs off that capacity for the weight of the hitch, and I'd bet dollars to doughnuts 1000 lbs is going to put you well over.
And then there's the trans... Good luck getting 8000-9000 lbs of rig moving on a hill without torching the clutch... And it's not going to be long for this world once you do.
Forgot to mention... the frontal area limitation of the Ranger's towing capacity is 50 square feet... That limits you to a camper that's 7' wide and roughly 7-8 feet tall. I suspect that camper is well above that... All in all, between the pin weight, gross weight, frontal area of the camper, and the transmission in your truck, it's going to be WAY out-classed by that camper, bordering on dangerous. Also keep in mind, you're putting more than just yourselves at risk... There are other people sharing the roads with you. From a strictly mechanical standpoint, your rig really isn't up to the task. But from a safety perspective, it's just plain not the right tool for the jobs. Heck, many 1/2-ton full size trucks wouldn't be up for it either, but it would be a heck of a lot safer.
