when hubs are locked, or 4wd is engaged, there should be no distinct noises what-so-ever. apart from normal everyday noises, which suzuki's are notorious for.
even if the transfer is in 2wd, and the hubs are locked, the entire drivetrain will be turning. the hubs lock the driveshafts to the wheels, in turn spinning the diff, and the front driveshaft to the transfer. this is different in a sense that the tyres are driving the front drivetrain. so if this is the case, you might want to pull off your locking hubs and give them a good clean and service. while they are off, check the locking ring is still good, and that the splines on the end of the shaft are still good.
if your hubs are good and working, then it might be time to check the CV joints. a good tell tail sign of where a CV might have gone bad is a broken or torn CV boot. this will let out all the grear, and let in dirt, mud and water, which, is NOT good for the CV joint. this will accelerate the wear, and ultimately lead to failure of the joint. sometimes a CV joint can be worn or in bad shape, and not make any noise, but can have excessive movement in the shafts. or, more commonly, the CV joints will develop a clicking noise when turning in 4wd, or under power when in 4wd. (this can also happen in 2wd with the hubs locked). this is more so on the outer CVs, as they not only have to deal with the up and down movement when the suspension cycles, they all have to deal with left right steering. so making sure the CV boots are intact, and the CV joint is good tight and clean, then all should be good.
if the noise is still there, and you have checked the hubs and CVs, then it could be a problem with the front diff. inside the front diff, there are 5 bearings. if any of these are worn, there may be excessive movement in the diff centre. bearings can develop all kinds of weird noises, from squeeling, to grinding, to ticking. cheack to see if there are no oil leaks from the front diff, as this can be just a worn oil seal, or a worn bearing allowing the shaft to have excess movement, in turn wearing the seal out. you can also check, by grabbing the axles where they enter the housing, and giving them a good shake, making sure there isn't too much movement, or looseness. you can also test out to see if the bearings are still good or not by turning the shafts by hand. this is done with transfer in neutral, and hubs UNLOCKED. turn the shafts by hand, and the shafts should turn freely, and smoothly. if you turn the shafts, and they feel course or as if something is grinding, then you might want to look into the bearings.
usually on track-kicks, the previous owners have never been wheeling, or ever needed to engage the hubs or 4wd system. this can leave the top of the diff 'dry' as the diff centre does not rotate, or get lubricated properly. this is why manufacturers suggest locking the hubs in 2wd and driving around for a certain distance. this will keep the crown wheel and pinion gear lubricated, and will not leave the top dry. the pinion shaft inside the diff has 2 bearings supporting it, and if the diff is not lubricated properly, then the outer bearing can get a bit dry, and might stick. this can cause bearings to fail, or not run smoothly, resulting in failure in the end.
also, your crown wheel might be cracked, or a tooth chipped, resulting in some noise. if this is the case, you may not be able to realise it until the diff is spinning at a much faster rate than you can turn with your hand, suck as driving in HI4. the noise may become louder as speed increases, and the pitch may also develop into a whine at hicher speeds. if a crown wheel or pinion gear is chipped, it is not good as there may be pieces of metal loose inside the diff housing, and may contribute to more damage.
