That is interesting, because if it were a clutch issue, it should do it no matter what gear, or what 4x position it is in.
Im thinking you would be good to remove it all and check it over real good. I had a weird issue pop up after replacing the clutch on my jeep, and come to find out I left one bolt finger tight on the flywheel. Didnt think that would cause my problem, but it did.
Maybe your transfer case linkage?