Originally Posted by Toreador4x4
ALSO if you went from a 7.5 to an 8.8, the 8.8 has 108 teeth on the tone ring and a 7.5 has 102 teeth. this will increase your speedometer by 5.8% .
Exactly right and thanks for reminding me, Justin. I remember seeing that choice option in the NGS setup. So, if a 98~00 8.8 axle gets regeared or a 98~00 7.5 axle gets regeared, the speedometer calibration would not affected. But if the entire axle assembly in a 98~00 is swapped from 7.5 to 8.8 or vice versa, the tone ring difference must be taken into account.