Welcome to the forums.

If the transmission is still under warranty, I'd get it in ASAP.

If possible, it might help us if you can tell us which transmission (CVT or 6 speed auto), and post any error codes.

Sometimes whining on startup is caused by something belt driven, like the alternator, water pump, power steering, a/c compressor, etc. so if it hasn't been done already the belt could be removed and the engine run briefly to see if the whining goes away.

 

The sound you heard when you first start your vehicle is probably not the transmission. I guess I could be wrong, but your transmission doesn’t really start “working” until you put it in gear. Granted, the fluid will start warming up and moving through the system a little bit, but it doesn’t really do much work until you put it into gear. I think it’s more likely that the belt or one of the pulleys is making that sound.

none of the problems you described are transmission slipping. Transmission slipping would be when you’re driving in motion, and when the transmission changes from one gear to the next (or changes the pulley ratio in a CVT), the RPMS go up but it doesn’t catch the “gear”, and you loose speed or stay the same speed because the transmission isn’t engaged and propelling your car further. Usually what happens is after a few or several seconds, it finally catches and there’s a sort of jerk forward feeling, sometimes accompanied by a change in RPM.

 

 

My story, maybe not relevant. I had my last Caravan tranny rebuilt at about 140,000 miles (actually was bad). A few months later the tranny started "slipping" . They had it back in the shop many times and even installed a different rebuilt tranny. The actual problem was a $30 intermittent defective throttle position sensor (no codes). Due to all of the computer controlled drivetrain activities, the defective TPS created slipping-like symptoms. The shop owner drove with me for an hour with scan tool/scope to diagnose the problem.

Lesson: be careful to avoid diagnosing with preconceived "blinders" on and overlook the obvious.

 

Daughter had whining, which progressed into the alternator locking up and shutting down the engine from drag.

 

My daughter had whining too. I told her to get over it. Lol