Vibration and/or slippage feel on slow right turn

You could be experiencing a slippage from the transfer-case as the clutch in there has to give or "slip" or drive-line binding could occur. most of the time this can be corrected just by servicing the transfer case and using the proper fluid and additive for the viscus clutches inside. The proper fluid is "autotrac fluid" from any g.m. dealer. its not cheap but must be used because of this condition. You could also be experiencing tire slipage because the clutch may not slip as it should. once again check and or service tha transfer case. To check the fluid you have to remove the "fill" plug on the rear of the transfer-case. This is the upper plug. Some are an allen hole requiring an allen wrench and some have a big hex bolt head aprox.1 1/4" in diameter. after removing the plug you should be able to feel the fluid on your finger if you stick it in there. autotrac fluid is clear in color and should not smell burn't. Good luck