Car shifts fine at Wot, but not under normal load

[jimmy9482]

Hey, My tranny started to slip yesterterday going into 3rd, so drove it slow home , today i went out to drive it again and did the same, but i got on it and after 2nd gear was past 3k rpms it would shift into 3 and 4th would come in jus like nothings wrong,after the car is in 3rd acts alright like highway drivng,but if I come to a stop i have to either give it enough gas so 2nd gear is spun past 2500 to 3000 rpms, or leave it in second and manually shift into drive at 3,000rpms, I took it to my tranny guy and he said the internals were fine that it was something electronic, all solenoids in the tranny are 3 months old, im getting a ses light but its just for 02 sensors, My tranny fluid is full and bright red, anyone help