Could it be less than a transmission problem or is it just that??

What is your question?

Ive had the car for about 4 yrs now but have recently started fixing it up. everything has been working well up until about two weeks ago. I can start the car and change it into reverse, drive, or neutral and it changes like it should, but when I start to drive the car, initially it rides smooth til the car gets to about 25mph and then it begans to rev up. Im not educated like that when it comes to cars but Im in the process of learning...I changed the modulator valve (unsure if I did it right and unsure of how to check it to make sure), another guy told me it could just be an electrical problem, then I heard it could be my torque convertor, and lastly, I was told my transmission could be about to go out. I was told to change the strainer in the transmission and service the fluid, which I did to no avail. Not quite sure what it could be. O yeah, someone else said it could be the solenoid. Can anyone steer me in the right direction please???!!!