my 90 thirds (3.8)l engine... the o.d.only reaches 30 mph than slips,hot or cold

What is your question?

I can get up as fast as needed in regular drive but the o.d. won't kick in at all whether dropping the gear or picking up the gear and runs fine until approx. .30mph then I've gotta shift to just drive if I wanna speed up and not rev the motor and go nowhere. fluid is clean and fine