Hi Scotyy. My father has a Santa Fe 2013 2.0T, 130k km (of course it is burning oil even though we changed it every 5000 km. Now it is done each 8000 km because it is 90% highway. He owns it since 40,000 km). After it wasn't driven for 2 months the transmission started to shift ruff. It was shifting perfectly before that. It is getting worse and worse.

I thought that over time heavy particles all settled but hoped to return to normal but it seems not to be the case. Transmission fluid was never changed because I can't convince my father to do this.

I asked a couple of mechanics and they told me that the 6 speed on this SantaFe are very good and it usually the engine is the one to go first. Not sure how a 2 moths of no use could cause this. 

Before it was pulling strong and the torque converter was locking and it was as if driving a manual. Now it feels like old automatic transmission where torque converter does not lock.