hi just a question. since series do not have a center locking diff, does it mean that the car will be immobile if one wheel loses grip (cos all power from engine goes to that wheel) even thou we are in 4wd low range?

No, both axles will still get drive. Not only does it not have a centre locking diff, it doesn't have a centre diff at all!! That's why you shouldn't drive on dry roads with 4wd, as the transmission will wind up and cause damage it itself, there being no centre diff to let the axles vary in speed.