What happens if...

[DEFYANT]

.....you rebuild a stock 4R70W transmission and install it into a Marauder with programing for a 4R75W transmission?

[Zack]

The OD light will flash.
The speedo will be WAY off as well.

The internal gear ratios and # of holes in the VSS sensor values in the software need to be changed.
Super simple to do.