I have a question about the tune required after upgrading to 4.10s in my 2011 Mustang GT.

Here's the scenario.

Currently I'm running a 3.31 gear ratio and I want to upgrade to 4.10. As I understand it, I have to get a tune. Lets say later I want to switch to a different tune or I want to switch back to the stock tune for warranty work - or whatever - this part isn't the point. The point is, when I switch back to the stock tune, does my 4.10 fix go away until I switch back? Or does the gear ratio fix get saved one place and the engine tune get saved somewhere else... u know where I'm going?

Thanks

 

I called American Muscle today and asked if anything gets altered in the tune when you change rear end gears, they told me no. I went from 3.31s to 3.73s and just selected that ratio on my handheld when I uploaded my tune. It's only 1 file that you upload (unless things changed from '05 to '11, doubt it). The only thing I would think to be off if you are running a stock tune would be the speedo

Not sure if that's a help or not. I would suggest calling American Muscle to be 100% sure, they know their stuff and are very helpful