I have been having problems with teh tranny for a long time.

It shofts hard from 1st to 2nd. I did the flush and fill/and filter as per the service bulletin. It took about 1 week after to straighten out the problem. It is now 6 months later and it is doing it again.

I took it to a transmission shop, and it has code # 748
pressure control seliniod , electrical.

I know that the flush and fill was in the service bulletin, then if that wsnt the cause, it said to rebuild the valve body.

Any insights ?

If your pressure control solenoid is out then it's very likely your line pressure is too high, which is giving you the tough shifts and can also lead to premature tranny failure. Replace the PCS quick. If you also want to add some tranny life while it's in the shop, you might consider a transgo shift kit with a corvette servo... That's my plan when the funds become available...