Try shutter priority mode, the big S on the wheel on top. Then set your shutter speed with the thumb wheel on the right hand side and experiment with faster/slower shutter speeds. That should work.
I would set iso to auto too.
Make sure you have it set to continual focus as well and also most people use burst mode (continuous shooting). As above, you should set it to shutter mode, about 1/200th to 1/400th if you want to play it safe, or slower than 1/200th if you fancy a risk.
Ukaskew's motorsport guide stickied at the top of this section is the best place to start.
Make sure you have it set to continual focus
But more important than all of the above, use AI Focus or AFC? on Nikon, So its constantly Autofocusing, without this all of the above will not make a difference because nothing will be in focus.