I love this guy. I can tell this without even watching the video, and justly looking at that de-padded dash, those gauges crammed into the dash holes, and, most importantly, those three wall-light switches screwed into the dash. Those three switches and the guy's brain are now the computer that shifts the car.
See, our friend here had a truck with a manual transmission, but because of a herniated disc in his back, clutches and shifting weren't really a good option. So he got ahold of a 4-speed 4L80E automatic transmission, and with a bit of work (driveshaft shortened, crossmember added, height adjusted, etc) he got the transmission in. But without the transmission's computer.
See, that transmission came out in 1991, and like everything built since 1990, a little computer tells it what to do. Specifically, it relies on three solenoids to tell it when to shift and (with the assistance of the gear selector) what gear to shift into.
Our intrepid hacker here bypassed the computer by wiring those three switches to the pinouts of the transmission/computer cable, and uses two of them to tell the transmission what gear to shift into. The other is used for the overdrive lockout, I believe, and he just lets the pressure level input default to maximim, which means harsher shifts, but who cares. His car has no interior — clearly this is a man who can deal with a harsh shift.
This reminds me of a much, much simpler hack I did years ago on my Beetle. I used to have the semi-auto with the solenoid-actuated clutch, and the switch for the clutch inside the shifter broke. So, I wired up a little toggle switch, and mounted it on the shift knob. Click, clutch in, shift, click, clutch out. It was fun.
This guy, though, he's taken this idea all the way. And, as a by-product, he's made his dually pretty much un-stealable.