Quote Originally Posted by Holiday Jones View Post
Mine does the same thing. Right at 40mph there's a hum, but it is directly in proportion to throttle, like it's the motor. I am assuming from posts of those who have added aftermarket exhaust to the MDS hemi that say the motor is actually louder on 4 cylinders than 8 that it's the MDS system coming on. ?? Maybe someone who knows more about that can shed some light on it. But as far as I've read, 40mph is around where the MDS is supposed to engage
That's what I've heard, too. A Diablosport Intune I1000 will run you about $290, and it can download custom tunes from the web and install them on your ECU. Another handy feature is that it can turn off MDS (which a lot of people find to be kind of an annoyance). You might be able to find a shop that will do it for you without buying the device itself. Might be worth turning off your MDS, as a part of your troubleshooting efforts, but be aware that you'll probably see a drop in your MPG.
If you have custom exhaust and still use MDS, that might cause a drone. I've heard about guys who have deleted their resonator and get an obnoxious drone at highway speeds.
(I, myself, plan on cutting out the stock muffler and putting in a Flowmaster Super 44; haven't decided on deleting the reso yet, but that's for another thread.)
Hope I could help, and best of luck!

2005 JGC 5.7L
stock... for now 😉