Yesterday I Replaced both the external and internal trans filters. When I measured the Fluid that I drained, it was 8 1/2 Quarts. I refilled with almost 9 quarts.
The external filter was changed once before with no fluids added at 26K miles. Truck now has 48K miles on it.
My problem is I cannot get 2 consective readings that are the same on the dip stick. Get both high and low readings?
Should I just call it good or what?

 

The hatch marks on the dipstick are only 1 pint (1/2 qt) between high and low, so don't fret over the exact level too much. The system holds about 17 quarts, so a pint give or take is no biggie. Personally I would prefer to error on the low side.

As for checking it, make sure it is fully up to operating temperature when you check it, and check it with the engine running and transmission in Park. Using the cold hatch marks works in a pinch, but you will see a wider variation.

 

Yes, just call it good. Trannies work very well until they are completely too low which will usually show up as a wake-up call when it slips going around a sharp corner.