1990 suzuki diagram of front locking hubs - 1990 Suzuki Sidekick

all you have to do is disconnect the front hub locks
to remove the axles is a big job for no gain. even removing the front drive shaft gained nothing as all the action is in the front drive hubs
without them engaged is the same as removing the front axles

Your hubs may not be locking. With your hubs in the locked position, raise the front tires off the ground, manually rotate each front tire and see if the axle connected to the tire spins along with the tire. If not your hubs may not be locking the wheel to the axle. Good luck.

just make sure it dose not have manual front locking hubs where you have to turn the dial on each of the center hubs on the ft wheels to the lock position before shifting into 4wd

No noise should come from the front when you are driving on asphalt as you are in 2WD, right? If you have been using 4WD with the hubs locked on asphalt, then there's every chance that your CVs are shot. You are, of course, unlocking the hubs when you are only in 2WD aren't you? When the hubs are unlocked and the car is in 2WD, the CVs do absolutely nothing. With the hubs unlocked, and the front jacked up, spin the wheel and listen for noises, and grab the top and bottom of the wheel and wiggle it in and out and check for movement. If there's no noise and very little movement, then your bearings are unlikely to be the problem. These are taper roller bearings and can be adjusted.

hub seals are bad or vacuum hoses rotten

Your front wheel hub is not locking when you engage the 4WD stick. Maybe the hub was not correctly installed during your last wheel bearing repacking.

If your system works...

Engage, then lock.

It is not advisable to keep the hub locks engaged full time,,because it can cause premature wear,,or even damage,especialy if you drive over 30MPH 50kph

Hubs do quit working. Jack both front wheels off of the ground and lock the hubs but leave the transfer case in 2wd. If you spin one wheel the other should spin backwards. If not replace the hubs. If they do spin correctly, you may have a transfer case problem or a front chunk problem.

Perhaps replacing the hubs would fix the problem. Locking hub often sit unused if you are not a frequent user of 4x4. This lack of use leads to the hub being hard to turn and in need of replacement. http://consumerguideauto.howstuffworks.com/1990-to-1998-suzuki-sidekick.htm has examples of various aftermarket hubs, personally I think the Warn hubs are the best.