Did a similar full time to part time conversion on a Chevy Blazer once. Other than digging less ruts into a dirt driveway when turning, I noticed very little improvement in mileage or power. The only real difference was that I had to get my feet all muddy to get into 4wd because I had installed manual hubs.
My oil line fix
My 100k stopped odometer fix
Brace for impact, I'm in a "modifying mood". Massive thread count inbound.