the planet gears do the torque split front rear, the viscous coupling does the locking

so what you need to do is fit a solid centre viscous, it's the big cylinder thing and it's easy enough to get to, but welding it up is going to be much harder as they are made of aliminum i think

you could just get the fluid pumped up or drill a hole into it to let the fluid out and then fill it up with other stuff