1998 Automatic V6 - no 3rd gear

I have been having shifting issues for about a month, though all gears. I was getting the code P720. All repair shops (and dealerships) said that the transmission is bad and needs to be replaced. $3000+. Long story short, checked out all the solenoids. Found that the Shift Solenoid Assembly was plugged, which gave me back 2nd and 4th gear and a smoother reverse. Cleaned out the Linear solenoid assembly. That gave me perfect shifting through all gears except 3rd. Seems to be plugged somewhere as the clutch wants to grab, but not quite. Are there any other filters (more like a 3mm screen) within the transmission? Thank you for your time.

Dennis