Look at your LST operation guide page 8. You will see: IMPORTANT: Always reinstall...... That part you see is only a gasket. Mugen sell them by the pack. Everytiime to take the diffs apart you may want to replace it. So look for Mugen seiki parst and find the differental gaskets. If you buy from Losi you will have to buy the whole rebuild kit, which is nuts. Buy the pack of gaskets from mugen allows you to take the diffs apart and try different weights on the diff oil.