Best methods to lock a center diff??

[JERRY2KONE]

Well it all depends on whats available for your particular vehicle. Some manufacturers make a spool for them, which acts like a stright through axle. You could also try using several different substances in order to achieve your goal. You can try using a very thick grease which would still leave you a slight slipage, or even go all out and use something like gorilla glue in the diff cup. Of course it would be vertually impossible to change it back to a limited slip diff if you lock it up with glue. Acquiring some kind of spool or even making one yourself would be your best bet I would think.

[florianz]

you can take hot glue. When used on oily gears, it can be removed later.

or you get a torsen diff (or lsd-diff by losi, xray etc.). a torsen (I have it in the center) locks under load, up to 80 %.