Transmission not down shifting
 

I have a 1999 S80 T6, The transmission has a few problems, it does not shift into 4th gear and does not down shift. I can manually shift from 1-3 one or two times before it gets stuck in 3rd gear. I use it on short trips, but because the check engine light is on it will not pass inspection. Is there any way to change those solenoids if thats whats needed with out dropping the engine and transmission.