Gear Break-In Procedure

Toyota Open DifferentialToyota differentials are no different than other vehicles... in regards to there care and maintenance. If you've just bought a locker or changed the gear ratio in your Toyota differential, you'll want to pay close attention to how you drive it for the first few hundred miles.

Big Mike from Marlin Crawler outlines the basics when it comes to breaking in your new diff.

Most importantly of course is making sure that you have fluid in your differential. If it's the right type of fluid, that's even better. Toyota differentials do well with a 80w-90 gear oil mixture. Depending on how much you paid for your gear or locker and how much it cost to get them installed will usually dictate what brand of gear oil you will buy.

When I bought a $200 automatic locker and installed it myself, I used Wal-mart gear oil. If you pay $1000 plus for an electric or air locker, and get a $200 set of gears, you'll probably want to use something like Penzoil or similar name brand.

Here is Big Mike's list of do's and dont's:
http://www.marlincrawler.com/tech/differential-break-and-care-information