I found this video from Ashcroft Transmissions, regarding transfercase failures, ultimately leading to transmission failures. Its interesting and will definitely effect when I lock my CDL off road, and how much I allow my wheels to spin. The interesting part starts @ 1:00. Moral of the story is don't allow to much wheel spin. When off road in slippery, low traction situations, lock the diff. The video states 5-10 seconds of varying power i.e. wheel spin in front and none in rear without the center differential locked could blow the center differential. When center differential is blown it acts as if its always locked, then your transmission will fail quickly.