Do you recommend any sealant like RTV on the gasket?

Using an RTV gasket maker or silicon gasket sealants with the transmission pan gasket depends on the factory's intended application. In this case, the 08C Aisin 8-speed automatic transmission pan gasket did not include RTV or sealants when assembled from the factory.

It is best to reproduce the factory-like sealing conditions for the most successfully sealed transmission pan on your 08C Aisin 8-speed. This typically means the mating surfaces should be clean of any old gasket materials, corrosion, and debris. This is typically best done with a plastic scraper-type tool. Ensure that the gasket mating surfaces are not scared or gouged during tool use. To ensure the gasket mating surfaces are free from imperfections, feel the mating surfaces with your finger and remove them as needed. Also, just before installing the new transmission pan with the gasket, a light amount of acetone, brake cleaner, or lacquer thinner on a CLEAN RAG can be used to remove all oil residues. Do not spray any area of the transmission with any of these solvents. Once these areas are wiped clean allow the mating surfaces to dry for about 2-3 min from these solvents, and then install the pan, gasket, and gasket spacers. This will give the best sealing condition for your Aisin 08C 8-speed automatic transmission pan gasket.