front end getting hot
 

I have a 1992 dodge dakota. My 4wheeldrive had quit working so I bypassed the 4wheel drive actuator. I added 80-90w oil to the front end to replace what I had lost. Now only after a few miles my differential cover gets very hot. Even after i put the actuator back the way it was it still gets hot. Did I use the right oil? Do i have bearings going out? i have no idea please help.