Here is a link to one of the previous threads in which towing capabilities, including that of an Explorer, are discussed:
http://www.trailmanorowners.com/foru...ead.php?t=1477
Adding a transmission oil cooler and 7-pin connector may be relatively easy to do. A hitch shop may be able to put on a heavier duty hitch for you in an afternoon. Converting your rear axle's gearing to a higher ratio, however, will be quite expensive - perhaps $2,500 to $3,000 or more - and that job requires an expert's touch to produce a satisfactory result. Like you we were faced with some of the same problems with our previous tow vehicle, a Ford F-150 that did not come from the factory with a towing package. I added a transmission oil cooler, heavy-duty hitch, brake controller and wiring hookup for a trailer but that still didn't make the truck equal to one equipped with a factory-equipped towing package. The F-150 pulled our 3124KS well on level grades but struggled when it came to steep grades (such as our Hwy. 5's pass in the "Grapevine" area). Having learned from those experiences, we moved on to a truck equipped with a towing package and a little more horsepower (at the sacrifice of gas mileage, I'm saddened to say).
Where is RockyMtnRay? He's our local expert on the capabilities of tow vehicles.