Every SD40 manufactured in 2000 and later was DCC friendly. The simple clue is the earlier SD40's that are in blue boxes are not DCC ready. The SD40's that are in green boxes are DCC ready. This does not work with the SD45's though. They need to be post 2000 as well, but the NON DCC ready version were released in the Green boxes as was the non DCC ready C30-7's. For the latter units you can check the Kato website. For the earlier units, I captured the information in a spreadsheet when I built a database to store my train information in.