I have a new truck that I have driven a couple of times and want to change the center diff fluid to 500k weight. I have looked for videos, but only find rebuilding diffs, not a simple fluid change.

My question is do I need to completely break it all down? Do I simply open the case and add the new fluid?

Any known tutorials would also be great.

Thanks for the help.

My recommendation, remove the center diff. Now test it everway possible. Rotate the outputs back and forth, try pushing them in and out, determine if it needs any shimming before taking it apart. If it does, go through the shimming process before adding the fluid you want to run.

Changing the fluid. You didn’t mention the vehicle you have but every center diff equipped vehicle has the diff filled with either silicone fluid or grease. Simply opening up the diff and adding the fluid of your choice is not an option. If the diff was filled with silicone fluid you have it easy, simply open it up and turn the diff cup upside down on some paper towels and let it drain out. There’s no need to pull all the gears out of the diff cup as the light coating of fluid that remains on them doesn’t have a huge impact, but if you want to go nuts then go ahead.

If the diff was filled with grease you do need to pull all the gears out. Once out, wipe all the grease off or hose them down with brake clean to get rid of the grease. Then put it all back together for filling.

Filling. Take a look at your ring gear, see that gear in the middle of it? That gear will take up space inside the diff cup meaning you don’t have to fill to the very top. You do want a little bit of fluid to be squeezed out when putting it together so if you don’t get any of that add a little more so you know it’s full. A diff that’s not full will act like it has a lighter weight fluid in it. Air bubbles also make the fluid act lighter than it is because air bubbles mean it’s not full. So fill almost to the top, let it sit so air bubbles will rise to the top before bolting it back together.