wont hit passing gears 3,4 on 1996 Chevrolet Suburban 1500

no codes cames up on coder reader but i left the gas station and i had a trailer on the back .then it just stop hitting its passing gears i changed the strainer still no change /speed sensor no change so now ..i may have to change my trans.shift sensor silonoids u think this will solve my shifting problems? can u tell me where the shift sensors r located. is it where th strainer on trans?where? please help..

shift solonoids are inside the pan, but get a tranny shop to test drive it to verify the problem.