When i first bought the car, it was low on transmission fluid. I added four quarts and for awhile everything seem alright. One day i check the car and it was leaking fluid between the engine and transmission, (mainly from the flywheel cover or dust cover). Went underneath the car and put some high temp RTV sealant on the cover to help it seal. No leaking unless the transmission is hot usually been driving for bout 20 minutes. Notice the fluid is low again and im getting tired of buying a quart here and there just to get me going. Also starting to notice smoke is showing mainly because the fluid is dripping on the exhaust. A mechanic told me the seal is probably dry because of low transmission fluid. He told me to fill the transmission up which usually takes about 12 to 13 quarts and add a stop leak to swell the seal. Sounds like a good idea? The transmission is probably overheating which caused the leak. Any suggestions would help?