Flat towing 2003 Ford Explorer sport trac

The tow kit is nothing more than an LED light, a plug, a template for mounting the gizmo, and the safety stickers.

Basically the dealer plugs the Neutral Tow Kit into a socket under the dashboard, and then they ”flash” the vehicle’s computer to tell the 4 wheel drive transfer case to shift into neutral when you step on the brake pedal and push the 4×4 button, with the transmission in neutral.

The key is having a dealer, "Flash" the ECM to enable Neutral in the Electronic Transfer Case. Putting it into Neutral is a rigamarole of gestures as noted above. The visible part of the "Kit" is an LED that lights to confirm that you did the rigamarole correctly, placing the TC in Neutral. There are a few writeups about it around the WEB.

Do some more research on Sport Trac. I think some of those, some years, had the Neutral Tow capability as delivered.

DON'T take my word for this. The conversion I read about was a 4x4 Explorer about that age.

We towed a '03 ST 4X4 4.0 V-6 for almost 100,000 miles. The harness & light make it easier as on the '03 no flash was done on ours when installed at the Ford dealer we bought the Sport Trac from in '05 with 15,000 miles on it. The kit was installed in less than 10 minutes and the dealer didn't even know what it was. We gave them the part number and they ordered it in for the day we picked it up. The part at the time was $27 with the "installation" running the price up to about $110. How many miles does your Sport Trac have on it? Ours had 157,000 plus 100,000 towed, not showing. After our fall check up on the Sport Trac last year, on start up our independent mechanic pointed out the timing chains (3) starting to rattle. $3000 to replace just the chains, as the engine had to be pulled, but if they "dropped" $6-7000 for a factory long block, which all of the old parts would be reinstalled. He told us to start "shopping for a new toad in earnest" as this was a problem on that vintage 4.0 V-6. The rattling seemed to start lasting longer each with each start, but then I might have been just a touch paranoid. We bought our current 2014 Flex in Mobile AL about 6 weeks later and had it set up and wired to tow for around $1250. New Blue OX Baseplate, coiled cord to coach, wiring, diodes, Patriot breakaway wiring including cable, adapter brackets Demco to Blue Ox and labor.

Teacher's Pet wrote:
...$3000 to replace just the chains, as the engine had to be pulled, but if they "dropped" $6-7000 for a factory long block, which all of the old parts would be reinstalled...this was a problem on that vintage 4.0 V-6. The rattling seemed to start lasting longer each with each start, but then I might have been just a touch paranoid...

You weren't paranoid. The automotive forums have a lot of these stories. My family just sold an '05 Explorer as a basket case because of Chains.

Ford had this 4.0 V6 Pushrod Engine. Ford of Germany said "We can hop this thing up with Overhead Camshafts." And they did. In a Vee-Design engine, one cylinder bank is a little forward of the other. To make a "shorter" engine, Ford of Germany put the Cam Drive of the "forward" bank on the REAR of the engine, using what would be the pushrod camshaft as a jackshaft to drive it. Just fine till you need to fix it! I don't know if the chain can be replaced just by removing the transmission either. Probably no clearance to the firewall. I know the flywheel/flex plate has to come off too, because of the cam drive having to reach down to the original camshaft gallery.

The Explorer to get is a 2006 V8 with the ZF Six-Speed Automatic...