It looks like you don't need a transit visa, but I would check with your nearest Brazilian Consulate:

This visa can be issued to individuals whose final destination is another country bearing an air ticket with a stop or connecting flight in a Brazilian airport that demands a new check-in while in Brazil. This means that if you are changing flights from companies that do not have codeshare agreements, you will have to exit the international area of the airport, going through Brazilian passport control, officially entering the country. Contact your airline to make sure if you will need to check-in for your connecting flight in Brazil before applying for a transit visa.

http://miami.itamaraty.gov.br/en-us/transit_visa.xml