Terri;

Definetly don't put anything in that crack. Woodfiller is made to fill not stop cracks.. also these old cowboy tricks tend to work most the time but some can be very dangerous.

IF that would filler gets wet it could expand and then put pressure on the crack. P8nt is right. Just live it to a pro..

Let me know what happened since I am so late in getting back to you..