1989 automatic transmission fluid problem

It sounds like what may have happened is that when you drained the old fluid out you may have just drained what was in the pan. The fluid in the pan is usually less than half the total amount of fluid in the transmission. To get all the fluid out you have to run it out through the cooling lines that go out to the radiator. You need to be simultaneously adding fluid during this process so that the trans always has fluid. You can tell when all the old fluid has been pumped out by noting the color of the fluid. The old fluid will be darker looking initially and then it will change to a bright red or pink color as the new fluid comes through. Whatever you do, don't run the transmission with too much fluid as this can really damage it. Hope this helps!