I agree with what Derek said regarding dropping the pan and changing the filter and the approximately 6 quarts of fluid and then see how it reacts.
Don't have it flushed by a shop. That caused me more trouble than it was worth. required a complete trans rebuild after the flush at about 80K miles.
You may need a complete teardown and rebuild but it would be worth just dropping the pan and replacing the filter and the fluid that is lost when doing that. Just to see. It's not that expensive if your doing it yourself or even at a shop that your comfortable with.
I made the mistake that believing a trans with only 78K or so miles would tolerate a complete flush.
Damn, was I wrong. If you've owned the car since new and had the trans flushed, say every 25 - 30k then maybe you can avoid a major problem.
But having it flushed with a machine for the first time at 70-80K is not a good recipe. Other than a recipe for failure.
Since the rebuild, and after installing a drain plug in the trans pan, I drop the fluid (about 6 or 7 qt's comes out) every 2 years based on my driving habits and am hoping that I'll not have to have it dissembled and rebuilt again while I have the vehicle.
Prior to the Trans Flush all was good. After it it started what I would call "Wheel Hopping" during hard acceleration while trying to get into traffic. While sitting at idle waiting for that spot where you can jump into the open spot, the drivetrain would jump uncontrollably and the wheels would actually hop under hard acceleration from a stop.
It was unnerving and felt destructive. Had to bring it to a reputable trans rebuilder and let them bend me over. They dropped the cradle and trans, then noticed my rear trans mount needed replacement (cost for part $600.00) also while trans and cradle was out of the way the brake lines needed replacing from master cylinder to front and back wheels. Used Nickle Copper lines for another $400.00.
Then when all was said and done and ready for pick up, paid the rental car company $600.00 and noticed the front fender was dented from the engine cradle they used and the rear quarter panel was scratched from repeatedly dragging the overhead air hose over the car.
That required a conversation that the owner did not want to have, but ultimately paid MY body man to fix it.
One month without the car and more money than I care to admit was spent.
I'm sure this is more than you or anybody else on the forum wanted to read but I had nothing else to do.