Conversation Between Mark Kovalsky and 03EB_EB_inNY

No, it will not. There should be a switch on the transfer case that the PCM reads to know when it is in 4x4 low. That's only to change the shift schedules to the low range, the engine doesn't care if it is in low or high range.

For a reason that I never knew on some 4x4 trucks the output speed sensor moves from the trans to the transfer case. The speedometer signal should come from the sensor on the rear axle, so high or low range won't matter.

Mark,
I currently have a 2003 4x2 Expedition with a 4r70w trans and I am looking to convert it to a 4x4. The one thing that I am not sure of, and hoping you might be able to help with, If i do the conversion using a 100% manual t-case (atlas 4 speed) will it throw the engines computer into a limp mode? The 4x4 version of my truck has a output shaft speed sensor in the transfer case, is that to recalibrate the speedometer when in four wheel low?

Thank You,
Joshua