To summarize what we've discussed here, omitting the technical details:
The tongue weight of a travel trailer is the result of how the trailer is loaded, and a properly loaded trailer will have about 60% of the weight ahead of the axle and 40% of the weight behind the axle. When loaded this way, a typical trailer will have around 15% of its weight on the tongue. It's not the light tongue weight, per se, that causes sway. It's the improperly loaded trailer with too much weight in the back that is the problem. A Weight distributing hitch (WDH) does nothing to change how the trailer is loaded. Besides ensuring proper loading of the trailer, tongue weight is also important to determine whether the TV receiver is adequate for the trailer.
WDH apply leverage between the towing vehicle and trailer causing the tongue weight to be carried by all axles of the tow vehicle and trailer. This allows trailers with greater tongue weights to be towed and results in a more level ride which reduces stress on the rear of the tow vehicle and provides greater steering and brake control.
A WDH does little to reduce sway. Use of one of the various types of sway control, with or without a WDH, is recommended if sway if a problem. Some WDH, such as Equal-i-zer, have an integral sway control.
Not all vehicles or all trailers are designed to be used with WDH. Check your owners manual.
