I have a 700R4 in an older Chevy car.
It shifts from 1st to 2nd at 5mph, even at wide open throttle. And won't manually downshift until 5mph.
TV cable works fine & is adjusted correctly. (Read: I don't want more TV cable advice)
Did a pressure check. Reverse, 1st, and 2nd should have higher pressure at full TV cable. Reverse is OK but 1st and 2nd had no change. Stays at 115lb.
Narrowed the problem to the valve body. Which valve or where is the first place I should look for trouble when I pull tranny from car and remove valve body?

 

if you have no change with adjustment its probably a TV valve stuck medal contamination etc...