Eaton India explains M Locker differential on OVERDRIVE 

This is true, but only if you are going slow which wouldn't be too dangerous. The Eaton has a safety feature that will not allow differential lockup when going faster than 18-20 M.P.H.

i need difflocker for the front diff of my 4x4 safari,kindly let me know whom to contact.

wow!! when can we get 1 ...fortuner?

So, if you are going around an icey or muddy turn, and you give it too much throttle, the rear will lock if the wheels brake traction with the road? That would be dangerous.