To keep the new transmission alive, you need to keep it cool and shift it correctly in the burnout box. Transmission fluid will start to burn, change color, and smell when it gets hot. You can prevent damage by checking the fluid after each run. If it is burning, you'll need to run the engine to pump the fluid through the cooler. If the fluid is overheating on the street, you'll need to make sure you have an adequate oil cooler. Change the fluid with a brand-name Dexron/Mercon 5 at 25,000 miles on the street or with a Type F racing fluid between seasons if you are on the track.