07 Impreza, 2.0 automatic help needed.
 

Guys a little help?
I have an 07 Impreza WRX, 2.0L automatic, non-turbo. Recently we got a problem with it where it would take it into high revs (around 4/5k) to switch from 3rd to 4th gear. We were told this was a problem with the transmission oil and we got that changed. However the problem still persists and there is a high pitched whirring coming from the engine if the foot is let completely off the accelerator when going over 80km/h.
Any ideas as to what the problem could be and what course of action to take, we still have a year warranty left on it.

If it has warranty then get it straight into the dealers. Could be any number of things fron the box itself or the torque convertor

They're reluctant as always to do anything, it's probably the gear box but if that's gone its gone. They're probably wasting time until the warranty runs out.