Look closer at the hinge point on the right side of the tailgate. The spring itself is inside the tailgate.

 

He did not see a spring. He is not going to see a spring. He is convinced that there is a counter weight on his tailgate and will go to his grave arguing the point.

Case closed.

 

I looks like to me there is a torsion bar at the bottom on the right side.

 

Something on the bottom right side on mine too, I saw it when I was installing my pace edwards lock, I thought the tailgate seemed light but I also put the support shock thing from the dealer on the left side.Tailgate goes down so smooth and slowly and goes up like a feather.