Oldsmobile/Buick Repair: Transmission problem, buick park ave, transmission problem

Question
I recently purchased a 1999 Buick Park Ave Ultra. I believe the tranny is a 4T65E FWD with Supercharged 3.8L V-6. The tranny when first taking of at idle slips, after being underway 1-2 shift is smooth, 2-3 shift is smooth, but 3-4 shift (O/D?) bangs into gear, harder with harder acceleration. Downshift to pass exhibited hesitation at 3000 rpm and the SES light came on with the hard shift to follow. SES light remains lit. I recently found out these motors used a PCS (pressure control solenoid) which failed fairly frequently. The car has 108K on it and I am wondering if this sounds like a PCS issue or deeper transmission issue. I have not had the code read as yet.

Answer
I would suspect the PCS, UNLESS there is another code(s) stored.
I have seen the IAT and or ECT cause harsh 3/4 shifts. Also a P0128 can cause funny acting trannys.
Have them checked. If no diagnosis is avalible, please feel free to follow post back with code(s) and I'll help as much as possible.
I hope this helps
Good Luck
God Bless
Pawl