konstantinNeo

I have a 2000 Chevrolet Workhorse 30P, its a small size bread truck. Vortec 4.3l v6 with a 4L80E transmission. I bought the truck from the bread company itself and worked mostly on the engine, it runs. Last time I used this truck was 6 months ago. I have noticed that the transmission upshifted a bit hard but I never actually driven a 4l80e anything. Today I was trying to move the truck, the transmission sounded banging harshly and moving jerkingly, the vehicle advanced like 50 yards, reverse works good, nothing forward, now the transmission is not banging but if I rev the engine It will sorta try to move but only like at 5% power. What can I check electrically maybe? I have no OBD tool.