A little over a month ago, my mechanic accidentally put in dexron/mercon III in the 2000 Volvo V70 instead of the specialized Volvo fluid. Afterwards, it had lots of trouble shifting into 3rd gear. So... unfortunately he put in more dexron which made the problem worse.

The next day a transmission was ordered and last night it was installed. It did a great job going home but this morning it broke down only a mile from home on a steep incline.

My wife told me that when she got up the steep hill the transmission made some type of mechanical noise and then the whole car died. A few minutes later, I started it up to make sure the engine was okay. It was. However when I shifted it into gear the same crackling noise was there.

Before I had it towed 2 codes popped up.

P0712 - Transmission Fluid Temperature Sensor Circuit Low Input
P1618 - Communications Error

After it was towed, the vehicle was restarted on flat ground and seemed to run fine. However it only was put in gear for less than a mile according to the repair shop.

I'm a bit concerned that there may be an electronics issue. Possibly a loose connection or maybe some component is not bound or shielded the way it should be. If anyone here has any insights it would be greatly appreciated.