Shifts very hard in lower gears (automatic) and idles unevenly (high and low)

Hello, hard shifting can be caused by engine performance concerns - such as that which is causing the high and low uneven idling. This is because the "load" of the engine is changing, which can result in what would be "normal" shifting feeling more harsh. As a result, I would check this first. Disconnecting the battery will serve to only "reset" the engine's processor to "open loop" - meaning, the engine's processor briefly does not rely on data from engine performance components to create the proper running condition. When the engine "warms up", it goes into "closed loop", where it starts reading data and then adjusts component operation accordingly. Therefore, it definitely seems like an "input" to the engine's processor -- some kind of sensor or more than one -- is causing an engine performance issue. Or, there could be an air flow restriction or air flow leak causing irregular air to the engine, making it impossible for the engine's processor to compensate continually. You could still have a transmission concern, but at the same time - I'd look at engine performance first and then look at other possible issues with transmission shifting once the engine performance is resolved. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops