Altima 99 box failure to help urgently

How about friends good afternoon I want to help me with a fault I have a high 99 which began to skate the box first in the climbs or by accelerating sharply and later the fault increase no longer entered the changes later they changed oil and strange and now only a drive, neutral and the second It is interesting to knowing is whether these types of cars need a special scanner or if these boxes are controlled by some type of sensor or any electronic device or if the box is definitely an internal problem because they have told me the majority that is the box that is already bad and you have to open it or change it, greetings

The transmission of your car you have reparation is not afraid, it is only that you get the adequate profective specialist and that it is honest.