Re: High RPMs in Park
Agree, your high idle speed is probably whacking that trans pretty good.
Have you tried taking off the IAC (Idle Air Control) motor and cleaning it out, along with the mating holes in the Throttle Body?
If you haven't, that's where I'd start. BTW, if your IAC is integral valve/motor (motor housing crimped over the Aluminum valve body), then be carefull when using Gumout or other solvent not to get it up the shaft into the motor. Keep the valve end down when cleaning, so that doesn't happen. On some of the older ones you can pull 2 screws and separate the motor from the valve body, but I think yours may be too new for that.
The cleaning is simple to do if you haven't done it already, and the gasket usually stays on the Throttle Body, so just put it back on after cleaning.
May or may not be your problem, but its an easy and common place to start.