After driving about 10 miles, the tx won't shift into 1 st. It will jump back and forth between 1 st and 2 nd or just start in 2 nd (sluggish).

I have done filter and fluid change and complete system flush.

If shifted manually, it works fine. Whwn cold it works fine, I think it has a solenoid problem?

Also I understand that the 93 GC has a different transmission than the other models.

Any ideas out there?

Could be a few things a bad valve body, front band might be out of adjustment, front servo,Govenor solenoid. I would check the 1-2 shift valve in the valve body and 2-3. Could be a broken spring. If you access to a scan tool a good one that can read trans codes you might get some insight into what is going on. The connection is at the front of the console.