Ok, did a search. Read all the tech articles I could find. They all just say "Then refill the diff with gear oil" never saying what weight or preference. Gotta get down to the store and pick me up some oil for the D60 front and Corp14ff rear. Question is, what to get? Preferences? Synthetic? Semi-synthetic? Can I run the same weight front and back? Back has Detroit Locker, front has ARB. Inquiring minds want to know. By the way, I do like synthetics generally speaking but for the break in period for two new rebuilt diffs?