99 front shaft

I have a 99 siverado 6l. 4x4 (2000 model)and i am trying to extract the front shaft to change out the u-joint but because of limited clearance between the exhaust and the diff. I have to rotate the shaft after it is free from the front diff. to slide it forward to free it from the transfer case but I can't get it to rotate freely after I go thru the vehicle manual's instructions of putting the transfer case in neutral. Any ideas please .

Does it have the push button 4wheel drive? Does the ignition have to be on for the transfer case to be put in neutral? Just some thoughts...

Yes on both cases... I should have mentioned that it was a push button selection.