white_lion wrote:put on a nice heavy steel rear bumper, you'd be surprised how much of a difference some added weight behind the rear wheels could make, it settles the rear nicely, minimizes bouncing and also adds protection. it'll definitely be a lot better than that plastic sheit the rangers come with and also gives you the opportunity to incorporate some proper tow/recovery points seeing as they don't come equipped with any from the factory.
This is probably the most sensible and feasible answer yet. More practical than installing a lift-kit, and more stable than putting on an airbag set, etc.
Remember the leaf-springs in the back are meant to take heavy loads, so when unladen they tend to be a bit skittish when running over bumps. And remember the front torsion bars give a bit more play when unladen because they will flex a lot more in order to absorb bumps under heavy loads.
Another diesel member here, V2NR3.0, successfully installed an Iron bumper made by Team Loco, and he reported having a smoother ride with his Mazda BT-50 (same suspension and chassis as the Ranger) due to the weight of the iron itself (must weigh around 100-200lbs!!!)

Check out the thread
here...What a lot of folks don't realize is that when you test drive the Ford and BT50, the torsion bars are still brand new, nice and stiff from the factory. But as soon as they get broken in after the first 1000km's, they loosen up and the ride is no longer civil and smooth, it becomes harsher and bumpier.
If you're not happy with your truck and not willing to install an iron bumper, then my suggestion would be to sell the ranger and buy something with coil-springs - perhaps a Navara or a Hilux.