Is it the sort of knocking sound that makes you laugh then?.
jokes aside , maybe you have a woodpecker in your trunk?/ boot
i actually think that , it probably isnt your diff at all. Diffs , usually whine when they start to wear ,or are low of oil...
Its more likely as you are turning to mke the noise that it is something to do with a drive/ halfshaft.
The shaft from Diff to wheel. It could be sign of a wheel bearing on its way out either side? , a rear wheel starting to come loose!. Or your cv type joint showing wear between driveshaft and wheel . most likely to be this . Have a look arund the rubber dohnuts.. Good luck. Diffs are bolted in place and dont move so would knock at all times not only when turning . warm suggests bearings but prob wheel rather than diff.