I'm guessing that with everything electronic, a change in axle gears means a trip to the dealer to get the speedometer reading right again?

Or you could get one the tuners that does it and get to play with a plug in horsepower upgrade. You might be able to find an unlocked used one on Ebay. Other than that it's a trip to the dealer.

You don't need to recalibrate the speedometer with a gear change. It is only required when tire size is altered.

How would that be true? Tire diameter affects the reading just like the gear ratio difference will.

The rear wheel speed sensor reads off of a tone wheel mounted on the differential carrier that turns the same revolutions as the tire and wheel. It does not care how many times the pinion turns in every revolution of the wheel.

I believes that yellow is correct.

yup, speedometers on those trucks read off the rearend. Changing gears doesn't matter, I changed my 05 from 3.52 to 3.92 and speedometer was fine. Changing tire diameter is all that matters on those trucks. In the older truck where it reads off the transmission you have re-calibrate of you change anything down stream rear end or tires.

Darn I learned something new.

Yeah, thanks guys. I appreciate the help.

I have the Edge and I change my tire ratio with it