my 98 QX4's transfer case makes a huming noise when switched to 4wd auto or 4wd lock. makes the nosie wether it is moving or standing still. however it does not make the noise when it is in park or neutral while in 4wd auto or lock. is this normal noise or a bad bearing? does anyone else's QX4 make a huming noise when 4wd is switched on?

Hey yes I have the same question. my '99 QX4 has the same humming noise exactly the situations as you described. Not exactly sure if it's an okay noise or if it's a problem. I'm going to take a stab in the dark and say it's the transfer motor which is mounted on the back of the transfer case. Looks to me like it would be pretty easy to switch out with a new one but not sure on the complexities of that.

Anyone else have andy ideas what the noise might be and whether or not it's a normal noise?