All of India becoming Muslim majority is hard, so I've made the challenge easier.
My definition of North India includes every Indian state which isn't Telegana, Andhra Pradesh, Karnataka, Tamil Nadu and Kerala.
Are we including Odisha and Chhattisgarh? These have less Muslims than all of the South Indian states.
This is very hard. If you look at where Hinduism was strongest in northern India, it was where the Caste system was strongest; where there was as established a rigid class system in the society as possible. Some parts of North India have a higher percentage of Hindus than South India!
Couple of things to get a majority though:
1) More Sufi missionaries. Orthodox Islam, imported from Arabia, will not appeal to the common Indian villager. But an Islam integrated into the culture with Sufi traditions will work.
2) Longer rule. If the Caliphate conquered all of North India by the 800's, then the extra four hundred years could help.
3) Appeal to the brahmins to convert. If the brahmins in fact benefit from conversion (not in monetary or even political prestige terms but in local village prestige terms) then that would work. As long as there is a strong local system, Hinduism will flourish. The same is true for religions and cultures under many empires across the world. As long as the local system is there, then assimilation and conversion will not occur, at least in the full sense.