Caravans have two common issues pertaining to transmission fluid leaks. The transmission lines leak and the transmission pan gasket and transmission side cover gaskets tend to leak. Have it checked before you run the transmission low on fluid. I would suspect the transmission pan gasket is leaking, this is the most common repair for that vehicle and should run you approx. $125.00 parts and labor. If it is time to flush the transmission fluid do this as well, approx. $125.00 additional.