My Lancer has 112k miles and has been a great car but the transmission is possesed. It will shift very rough and get progressivly worse as you drive it. It will shift so hard, it feels like you are being hit from behind. If I let it go, I'm afraid it's going to break a motor mount.
If I pop the battery off and then reconnect, it will drive like a brand new car and shift smooth as silk. Then is will slowly start shifting rough again but very slightly and get worse, the more you drive it. The longer you drive it, the worse it gets. I have to pop the batter every 2 days or so to keep it driving smooth. I took it to the stealership and they charged me 200 bucks to change the fluid and re-flash the TCU but it still does it. Since it drives so smooth after a reset it can't be mechanical, right? Has anyone ever seen this? The car is totally stock with no mods.

 

something is most likely mechanically worn to cause it to alter its shift patterns so much.

likely a severely worn overdrive/reverse clutch housing.