Originally Posted by ninja_zx11

Both front and rear differentials work in a exactly same way.The reason why your rear wheels are turning in a opposite direction because your rear drive shaft is locked while the transmission is in park position and it cannot turn.
Your fronts are not behaving like rears because in a park position,transfer case clutch is open and front drive shaft can rotate freely even your transmission is locked.So when you try to rotate one of your front wheel,your front drive shaft starts turning before turning your other front wheel.If you hold your front drive shaft,i bet your counter wheel would spin in opposite direction.


Main difference between ISTA and snap on or similar tools besides the accuracy of reading codes is that ISTA guides you through test plans according your fault code.