From memory, the 1 kit has the lines to connect 3 or 4 breathers up. Front and rear diffs, tranny (not on 4runners tho) and t-casei should probably have one from how deep the water is that i drive into sometimes. so i watched a youtube video of how to hook it up to rear, but should front axle get one as well? would one kit cover both axles? not sure how it works...