Noise/vibration in 4wd

[Craigmoy]

Hey guys, I've just noticed my 2003 pathie has developed a new noise. When it's in auto or 4wd there is a buzzing sound from the rear end. Sounds like a fuel pump but I know it's not that. Any ideas? I'm thinking it's possibly the coil for the 4wd activation, but don't really have any idea

[mdmellott]

I'm assuming you have a LE model with an All-Mode 4WD transfer system. If the ATF is low, that could make the transfer motor whine. If the ATF is way past its service life, old and cruddy, that will wreak havoc on the entire system's components. The transfer case oil filter/strainer in the A/4WD transfer case should be removed and cleaned periodically, reinstalled with new O-ring gaskets, and the ATF changed regularly, per the maintenance schedule or even sooner on old-timers.