Try reducing things in the advanced graphics options too. and see if that reduces the amount of ram used. When autosculpting do small changes like a couple clicks at a time. Also I noticed if you spend too much time editing the vehicles the game stops responding.
tat's right, same thing used to happen to me, i jus turned down all t graphic options when autoscultping, nd it went fine, after tat, u can turn ur settings bak up