Most manufacturers provide specific schedules for transmission fluid flushes and replacements. A transmission flush is a ...

a transmission fluid flush or a simple drain and fill. A drain and fill — commonly referred to as a transmission fluid change — is the more basic job. As the name implies, it involves ...

If it's beneath them, a top-up or flush could be in order; the same if the fluid is gritty or dark. To add extra transmission fluid, you can simply use a funnel while the dipstick is removed.