best way to do a ATF drain & fill

My understanding that the AT has a very narrow tolerance of acceptable fluid level.

When I'm adding the ATF via the dipstick hole, how soon after does the fluid show properly on the dipstick? Can I just let the fluid settle down and then check the COOL range on the dipstick? Or do I have to start it up and shift thru all the gears before checking?

For some reason I feel very nervous about replacing the ATF, unlike changing the engine oil, I feel that if I screw up with the ATF, even subtle differences from the recommended level will f up the tranny..

 

You must shift through all of the gears and check the fluid while the engine is idling in park. It's not that bad, just add a little at a time til you get it right.

 

Right but how soon after pouring in the fluid, will the new fluid indicate on the dip stick?

Also whenever I'm adding a little bit new fluid, do I need to re-shift in order to check to new level?

 

I gauged how much I took out and added a bit less than that back in before I began checking, I believe that after the initial shift through, one can just check the level while the engine is running.