I have heard of other folks using silly putty but that was in 1/8 scales and smaller. I have also heard people using bee's wax. Heat it up to melt it then pour it in the diff and reassemble. To remove it that the ring gear off the diff and boil it in water because it floats. I have never tried it nor will I for the main reason that I like my diff to actually work for my driving style. besides it can't be good on the bearings. If you want to lock your diff then yeah, molten wax (even candle wax) in the diff will lock it tight. If this is to lock the diff in a Baja 5B then just forgo all this mess and buy a diff locker. It replaces the diff with a solid piece with the outdrives. No slippage at all.