you can not run your front shafts unless you remove the crownwheel from your front diff, basically if you do your car will be 4wd-locked diff and you WILL break stuff on a hard surface like tarseal or concrete, would probably be ok on gravel, been there, done that, thought it would be ok to leave my front shafts in just while putting the car onto a trailer....bang, front diff a big pile of metal. I now have front shafts in but have removed the front crownwheel so there is no connection between the front diff and the rest of the gearbox, the only real problem then is that the front crownwheel actually moves a lot of the gearbox oil around, kinda like a big paddle steamer wheel, and some people say they have problems with the box becomming hard to shift etc after a good hiding but I have never had any problems with that