2002 Toyota 4Runner Lurking when shifting to overdrive

Transmission problem
2002 Toyota 4Runner 6 cyl Four Wheel Drive Automatic

I recently had some routine maintenance done - this included oil change, brake inspection and changing of fluids. After this was finished I noticed that the truck had a lurking when I was driving. At first I thought maybe it was missing intermittently, then as I and my husband drove it, we assertained that it seemed to be lurking as it was supposed to be shifting in to overdrive right around 50mph. If we turned off the overdirve the lurking went away. We took it back to the dealer where we had the maintenance done and they thought that the transmission fluid had been overfilled, and drained it and refilled it to the appropriate level. We were told it should be better, but if not to return it to the dealer after a week. It seemed better for the first day or two, but was not and seemed no better since. We have returned it today and will see what they have to say. What do you think? We are concerned that maybe some permanent damage has been done to the transmission, by the overfill? Thank you.