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So there is a difference between pre and post '15 but I still don't understand why there's no (or less?) care for changes in the post 15 vehicles Is it because speed sensors on the front wheels measure absolute tire rotation as opposed to driveline rotation? Speed sensors in the earlier cars have them in the rears - or are these for ABS only?
The older cars compared speed/gear/rpms on a table in the computer. Any variation from the set amounts will trigger the CEL. It's such a close variant that a good burnout at the wrong time can trigger it. I did it twice on my '13 R/T, because I changed tire sizes.

After the 2nd one, I took it to the dealership and they flashed the TCM, did an update and I didn't have any more trouble with it.


The newer cars measure speed from the fronts and that table was removed from the computer.


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OK - think I get it now. Removing speed from the logic table leaves gear and rpm only which presumably makes compensation via a tuner (aftermarket or dealer) an easier challenge. This helps to explain what Zautomotive (Tazr manufacturer) told me when they said that even if I compensate for the ratio change by inputting a different tire height (taller height for a lower gear ratio and vice versa) this still would not account for the ratio change in the TCM. Presumably in a gear change, the TCM would "see" increased rpm (based on driveshaft speed ).

So....either flashing the TCM (tuner) or an outright replacement for a custom TCM like Jonny mentions is the way to address the "difference," am I getting this right?
 

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'15+ cars do not need anything but a new differential. There's no tune, no TCM needed just swap and go.

Your 13 only needs a hand held tuner like a DiabloSport i3 or Predator to make the change. There's no need for a custom TCM or any of that.

You're overthinking it and making it way more complex than it is.

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Got it. However (back to my original situation), when I do sell my '13 with a gear swap, that tuner needs to go with it or some sort of modified TCM.

Wanted to know the best, or most right way to do this. Thanks for the help!
 

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Got it. However (back to my original situation), when I do sell my '13 with a gear swap, that tuner needs to go with it or some sort of modified TCM.

Wanted to know the best, or most right way to do this. Thanks for the help!
Unless they intend on further modifying the car, they wouldn't need the hand held. Once it's changed, it's changed, until someone changes it back.

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