I had notice a burning oil smell i thought it is the oil filter or trans but when i opened the hood i found a small hose in the driver side leaking ,what caused this leak ?

 

The big plastic plug that goes into the differential that the hose connects to has a piece on the inside the swivels, if for what ever reason it flips you will get what appears as a constant leak. If you keep getting oil from the vent line, you may have to pull the plastic plug and check it out.