Hey all. My 07 3500 daully was giving me a slight vibration around 70 mph. I believe i isolated that to the transfer case, as there was slight play on the output shaft. So i removed it and tore it down giving it a good inspection. I replaced all the bearings and seals. Now as I'm reassembling it, I'm thinking i must be off. As i select through the shifter i can see 4wd hi and 4wd low. But at no point is the front output disengaged. That can't be correct. ... it isn't full time. The drive chain should not be engaged constantly ? So..... am i wrong and the chain is constantly under power, or have i missed something ? Thank you for the help. David.