Hey guys,
since i have my Saratoga, you can hear a whine or buzz noise, only in reverse, maybe coming from the torque converter. But only if the transmission hasn´t reached full operating temperature. It sounds like a bad power steering pump and is only noticable if you accelerate a bit, just touching the accelerator is enough to start the noise.
Of course, fluid and fluid level is OK, only used Mopar ATF+4 the whole life of the car. I also let the car run for at least 30 seconds (in warm condition), to let the TC run full of oil, pointless, i know.
But until the trans hasn´t been driven for arround 20 minutes, the buzz noise will appear every time.
A new TCU is on it´s way (as you already know

), but i can´t imagine why the noise just appears in Reverse.