It could be the actuator has reached the end of its travel. There could be extra play in the linkage. If you tighten up any extra free play at the closed throttle position, then the actuator would have more travel at the wide open position.
My answer is replacing your idle air control valve and oxygen sensor. Of course get the throttle body clean by with a throttle body cleaner or carburetor cleaner. Also check air filter makesure it's clean or new. But the really answer is the iac valve and oxygen sensor.
The chain in the transfer case can take a lot more abuse than 10 miles, even with a few sharp turns. Nothing popped, which means everything is fine. Just pay attention next time.
4HI or 4LO modes are only to be used in slippery conditions (snow, gravel, etc.), and you definitely don't want to drive high speed on firm pavement with transfer case and no center ...