Check Trans fluid when it's warm and engine running otherwise it will read high on the dipstick.
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Also you might not be getting all the old fluid out so I'd go by what the dipstick says. There is a specific method called for when checking fluid level:
Trans temp should be at normal level, 180-200 degrees.
Start in park, engine running.
Move through each gear, pausing for 3 seconds in each gear. (foot on brake of course)
Put it back in park.
Let engine idle for 3 minutes or more.
Without shutting off the engine, pull the dipstick and wipe it off.
Put the dipstick all the way in, wait 3 seconds, then pull it out and check the level.
Check both sides of the dipstick and read the lower level.
It needs to be in the HOT cross-checked area.