The rear will work better IMHO locked, than the front. Here's why..The front has coils and articulates much better than the leaf sprung rear, meaning it's less likely to pick a wheel up than the rear. So, with both front wheels being in contact with the ground and being open they will usually at least alternate pulling power based on the terrain. The rear when it picks a wheel up (if open) will spin that wheel free with zero help from the other. So, lock the rear and you always have at least one wheel pulling with the rear (more likely to be) tire in the air. May have done a crap job explaining it, but I ran several XJs locked on different ends and the rear locked/open front seemed to work best for me (other than dual arb's of course)...lol