Early Converter Engagement

[MNSubbie]

My wife's 03 Impala is shifting wierd these days, and I am seeking some advice:
When we first start drive it, it shifts OK----just OK. At first, all is OK except when it shifts out of 1st gear, it usually goes to 3rd, and then downshifts to second. Not a huge issue, but not quite the way it should be.
My bigger issue comes when we've driven it for a while........it shifts from 1st gear into 2nd with LockUp. Obviously, it kinda clunks into gear, and then all the other shifts are clunky because the converter is locked up for every shift. Since I don't dare drive it with a heavy foot, this all happens with very light throttle. (does not kill at stop signs)
I just changed filter and fluid, and put in some Seafoam. Got a 742 code once, but have not gone to a shop to pull other Trans Codes. Does this sound like the old PCS problem, or is it the TCC Solenoid, or is there some other switch that helps keep the Converter Unlocked in the lower gears?? Any/all advice and ideas would be appreciated. Thx

[maxwedge]

Welcome to AF. Get it scanned by a trans shop for all the codes they can also see what is happening internally relative to solenoid functions, any other way is guess work.