Meet Dan Mann, man. Dan The Man has a 1979 Chevy C30 dually. Unfortunately, he also has a herniated disk in his back, which meant that he had to make some changes to the transmission in his truck. Dan swapped out the standard SM465 manual for the GM 4L80E automatic transmission from his brother’s truck. He also took out the original computer controller and put in some light switches. Yes, light switches.
Hey, Dan, if you can, see a chiropractor, man.
Anyway, the 4L80E has four solenoids: torque converter lockup, line pressure, and two for shifting. Dan would need a computer for controlling line pressure so that just runs at maximum power, resulting in slightly harsher shifts. It isn’t too harsh for Dan to actually shift though because he controls the selected gear with either a floor shifter or the light switches. The remaining switch is his torque converter lockup.
It’s a bit hard to explain, but you have the best visual aid in the world. Check out this video of Dan’s truck in action with him explaining how everything works in more detail.