NXT TaskBot Modifications
The NXT TaskBot drives better than the TriBot, in my experience, but if you don't have the "NXT Educational Package" you are missing few pieces. However, you can use the modifications below to the driving base to still create a near-perfect driving platform.
Replace the Coaster Design
After Step 12 the TaskBot design asks for a third-wheel coaster design that can only be done using the Educational Edition. However, you can replace that coaster design with the one from the TriBot, as shown below. It is easier to build and should fit into the place where the original TaskBot coaster would go.