I was playing with the set screws so I hope that did screw it up. But what I did was turn them all the way in and back them off 1/8th of a turn. Then I went to the spring loaded screws and turned them in until it stoped the backed it off 4 turns on the second gear. I did the same for 3rd gear but backed it off 7 turns. I can not hear the truck shift Should you?

Pick the truck up and accelerate, you should hear the shifts.

That is pretty much it. Pick the truck up and then give it gas. You should hear it go through the gears.