2004 FWD Vue 3.5 Liter automatic transmission problem

The transmission with 98,000 miles on it was having trouble shifting into 4th gear. Had fluid changed which fixed the problem. Now, at 115,00 miles the problem has returned and is worse than before. When at the shift point, when driving at a normal speed before shifting into 4th, the whole car vibrates and "shimmies". If I am driving faster, there is only a slight vibration when it shifts. This only happens when shifting from 3rd to 4th. I am told to replace the filter (screen) the tranny has to be removed and taken apart. That being the case, a new tranny or rebuit would be my next choice instead. I love this SUV and want to keep it. I am going to change the fluid again and hope for the best.