Hi,
Sorry for the late reply. Just wanted to link to a fix in case someone stumbles across this post.
If you have the p1710 code, it is due to "torque converter turbine 2 speed signal circuit malfunction". This is a small HALL effect sensor bolted onto the back of the valve body in the 5eat. In the '08 and up cars it can be replaced individually without needing to replace the entire valve body.
I found the fix on subaruoutback forums here: https://www.subaruoutback.org/forums/109-gen-3-2005-2009/499945-repair-p1710-hard-shifts-5eat.html
The thread also has a couple of links where you can buy the sensor which is about $100 and looks identical to the stock sensor. There is also a DIY-type fix posted with a generic HALL efect sensor you can get from Amazon.
Hope this helps someone.