Animate a piece of the tank tread following its path at an even speed (roving keyframes will help). Use the loopOut expression so that it loops. Make enough duplicates and offset them in time so that you have a full tread movement. If you need to adjust the speed of this, precomp the whole set of tread layers and use time remapping.
Draw a mask path to mimic the tread shape , copy&paste it to the one of the tread link's position, enable 2D auto-orient on the layer. Takes about 10 nanoseconds. Then duplicate the layer and offset the timing. Add some wiggle to add a slight variatikon if necessary.
I know it's late....
but since it's a 2D front view, i would try and make a solid layer, put a VEGAS effect on top of it, draw a mask around the tanks track, then probabely do the whole animation of the tank
wheels and track (its a mask so you can animate separate vertex points). And when the whole animation is set and done i would precompose the track solid layer and move the
mask and effects to the PRECOMPOSED layer. Now back in the original layer i would put some effects (bevel emboss?) on the precomposed track.
I think you could skip the vegas and mask effect and do the shape layer with segemented stroke animation.
But VEGAS does give nice effect in this case.
yeah i know it's late