replacing diff fluids...
I also sprayed out the inside of the diff really well with some brake parts cleaner. I think I used like 1.5 cans of it. It doesnt hurt to do that while you have the covers off.
Here is a good write-up WOL did for changing fluid on his TJ.
http://www.4x4xplor.com/diff-service.html
Here is a good write-up WOL did for changing fluid on his TJ.
http://www.4x4xplor.com/diff-service.html


