I have 173k on my car and my tranny seems to be going from 1st to 3rd , I getting lack of power after that gear change. When I downshift it into 2nd it powers up again. Sometimes I will floor it at 65mph and it won't even downshift. These symptoms don't happen all the time , only sometimes. When the car is cold it runs fine until I drive for a half hour or so. My tranny oil seems to be redish brown. Any suggestions?