Ford Perfect,

The distance between the two terminals makes walking impossible...or at the very least, impractical. Fortunately, there is an interterminal bus system that runs between the terminals. There are two bus routes, ROUTE A and ROUTE B. They both essentially make a counter-clockwise loop around the terminals. The difference between the two is that after departing the Central terminal, ROUTE A bus goes all the way out to the Delta Shuttle/Marine Air Terminal. However, for your purposes, because you are going from Terminal D (Delta) to Terminal B (Central-Air Canada), you can take either bus without adding any extra time and I would get on the first one that shows up.

When you exit the gate area at Delta, go down the escalator towards baggage. There is a set of sliding doors directly in front of the bottom of the escalator...exit there and make a slight turn to the left and walk to the first curb (the inner one). The bus will pick up here. They are blue and white and on the front they have an electronic sign that clearly says ROUTE A or ROUTE B (again, you can take either). Between the two, I would expect one to show up within 5-10 minutes and the trip to the Central terminal will take no more than 5-10 minutes. Total time from Delta to Air Canada is 10 minutes (best case) to 20 minutes (worst case). The bus will make two stops at the Central terminal, yours would be the first.