The clicking when turning left on hard throttle is the front diff, i test by holding each front wheel one at a time and stabbing the throttle(be cautious of spinning rear wheels). It should make a bad clicking noise when you hold one wheel and not the other, so it's the diff. I used longer 2.5mmx12mm bolts on the diffs, takes a while to screw em in but the longer bolts along with 1 extra shim under each big diff gear and you're set for a long time. Less leaking too because the diff is assembled tight

EDIT: These are the screws i used, any brand will work, size is important
http://www.amainhobbies.com/product_...Head-Screws-10