I've got a D2 with a TrueTrac up front and a Detroit in the rear as well. As Red90 noted, the Detroit is a full locker, and when on solid ground you will hear it "pop" like that at times going around turns, especially if you are heavy on the pedal and hard in the turn.
Regarding CDL use, generally speaking if things are slippery and traction is poor, engaging the CDL is your best bet. However with the Detroit in the rear you will have situations when wheeling on firm ground (rock crawling as an example), where when turning tighttly the tires will not be able to slip sufficiently and that full lock from the Detroit in the rear is going to cause wind up. In these situations I will often try to disengage the CDL beforehand to prevent that, then work through the tight turn, and re-engage after if needed.
As a general rule though, if it is slippery ground it is best to avoid agressive wheel spinning without the CDL locked. The 2-piece cross pin in the LT230 transfer case is a fail point in those conditions. When its locked its not an issue. Ashcroft does have an upgrade for this though http://www.ashcroft-transmissions.co.uk/diy-rebuild-kits/lt230-rebuild-kits/hd-cross-pin.html
