Newbie Weird Automatic Transmission Issue

I just got a 2005 RX8 with the automatic transmission with 98k miles.

I have no history on it. It runs a drives nice.

However, if you really step on it will down shift (as it should).

But as your speed and rpms increase it won't automatically shift up like it should.

If you slow do to a stop and then take off again normally it will shift up just fine.

Also when it is wound out from kicking down, you can switch it over to manual mode and hit the up shift paddle and it will shift up fine.

So... what is causing it not to upshift automatically after it has kicked down???





Thanks!