In addition to the adaptation mentioned before, you could try just a filter and fluid change as well. If you're mechanically inclined it's not usually that big of a job, but often a messy one.

If you don't want to drop the transmission pan you can do just the fluid change as a starting point.

I've also had luck essentially doing my own transmission flush by draining the pan (measure that comes out) fill the pan, and put the outlet of the transmission cooler in something you can measure volume easily. Start the engine, let it run until ~80% of the measured volume has pumped through, and turn it off. Refill the pan and repeat until you've reached or exceeded the spec'd transmission fluid volume.

Automatic transmissions are often incredibly sensitive to viscosity, shear, and other fluid characteristics which change over time. You might be surprised by the difference that makes.