Sounds like an internal pressure problem in your transmission. Barring any check engine codes, you may be looking at a transmission overhaul.
At this point dont know if it is actually worth doing that. The car is not worth that much, so even a new (used) transmission might not be worth it. It is 15 years old, and I bought it cheap. I am going to change the fluid and see what happens. Then I will decie on what to do. Pulling out the transmission does not sound like a "fun" task.Sounds like an internal pressure problem in your transmission. Barring any check engine codes, you may be looking at a transmission overhaul.