Nissan Maxima 93´V6 3.0 Automatic Box Problems

Hello, I need help with my automatic box that my Nissan Maxima Model 93´ has, it has a 4 -speed RE4F02a box.
It was performed all the change of rings, seals, oring, oil (both of the box and the converter) and the filter of each part of it.
The box works correctly but when it reaches 100km x hour it begins to climb the turns as if the fourth does not enter.
The engine goes to 3000RPM at 120km to 140km with the 7000RPM engine.
Someone can guide me what will be or that I should check.
The valve box only changed the joints.
Wait any type of help.
Thank you so much.