the overdrive button is just another gear, there is no real reason to ever turn it off it wont do anything other than keep you from shifting into your final gear, generally called "overdrive" because the gear is less than 1 to 1 with the engine's turning.

TSC i assume is the traction control system, leave it on unless you are at the track then you may wish to get used to launching the car yourself.

SpectorV, I have a question or two, that hopefully you can answer for me. I wrote it in the 2005-2009 Mustang blog and it's called "ELECTRONIC TRANS". It's basically questions about the TSC button and the OVERDRIVE button, I see a few people viewed it but no one has made any comments.

Hey SpectorV, how's things going? Your car is a stick right? Do you have any knowledge or opinions on Stall Converters for Automatics?? Thinking about those and want to match up my 4.6 and 410 gears with an upcoming Super Charger.