That does not sound like your tranny. That sounds like you engine is giving your trans a workout. Probably missing, stumbling and backfiring. If you get the valve job done, this will involve removing and disassembling the head. Have the head checked for trueness, valves ground and seated and, of course new seals and guides. You will be happy with the results of this work. It will seem like a new car.
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.