wolverine666

My friend is driving a Legacy 2.5 My05 AT and having problems with the transmition (automatic). When he is driving straigt is ok, but when taking a turn or parking the back wheels are braking/sliping on the ground. He think its something with the electronic because the clutch that is in the back of the gearbox for the back wheels is always at 95% (showing on the diagnostic) but what taking a turn it must be lower than 95%. He changed some he said C valve for the back wheels clutch but same thing. Is it possible an other sensor or what?
Some suggestion???
Thanks