I was experiencing a sort of shudder/shaking with mine, also a few other problems like not going into park, and high revving between some shifts. I pulled the pan and found 2 metal pieces stuck to the magnet in the pan. I also pulled the valve body and a couple parts from the front band fell out. When the parts fell out it started going back into park again. I put the pieces back in the band and realized the band was way out of adjustment, and adjusted it. It was then that I emptied the pan and found the 2 metal pieces which appear to be pieces of the internal rings. That was the eff me moment, and so far I'm still working on either rebuilding or swapping it.
In your case I think I would first drain and drop the pan, change filter, look for anything stuck to the magnet, and adjust the bands. Depending on your mileage and since you are that far along it would probably pay to drop the valve body and put a valve body rebuild kit in it.
You can do all that without dropping the trans. Note: Use a wide drain pan, particularly when removing the valve body, a lot of additional fluid will come out.
Also I am not a Auto trans guy but some of the guys here have been helping me along, and they are quite knowledgeable.