How to Fill a Rear Differential

Filling a Rear Differential
1. Be sure the car is raised on four jack stands and is level. It will be more difficult to fill the differential if you've only got it raised in the rear.
2. Place an oil drain pan underneath the plug to catch any leaks or drips. Keep shop rags handy for any spills.
3. Check your service manual for the amount of fluid your differential needs, if you're completely refilling the system. Two quarts should be enough in most cases.
4.
Remove the spouts on the gear oil containers. Peel off seals, then replace spouts. Use side cutters (or any cutting tool you've got handy) to clip off the top of each spout.
5.
Remove the differential fill plug using a 3/8 inch drive ratchet with extension. (Some models may require a hex key or screwdriver, but the 3/8 inch is the most common plug design.)
6.
Take the gear oil container and fit the spout into the fill hole. Pour the fluid inside. You can gently squeeze the bottle to speed the process. Repeat with a second bottle if necessary.
7. Fill the differential until the fluid starts draining back out of the hole.
8. Clean and replace fill plug. Use lock tight (thread locker) to help seal if desired. You can see my eHow article 'How to Replace Rear Differential Fill Plug' for more information.
9. Take the car for a drive around the block to get the gear oil moving. When you return, check underneath for any leaks from the fill plug or differential cover.