[wolfox]

Well, I was thinking it was a dry knuckle, honestly. The hub rides on a wheel bearing in which the axle shaft protrudes from so it turns with engine torque, and then a set of bearings keep it aloft and spinning. Getting a look at it will involve nothing short of disassembly. And if you went that far - might as well poke in a new set of bearings and press them tight. Anyway -

Wiggle on your front tires, side to side, top to bottom, grasp it with a hug and lift it up and down. If it clunks, dollars to donuts you have a bad bearing, or at least, it is starting to go. If it's solid, lube the knuckles behind it on the inside, behind the brake rotor. Turning the wheel to either side sharply before doing this will give you some room to maneuver hands and your grease gun.

Barring that, follow the axle shafts themselves and see if there is indeed a locking yoke and lube that. If this is the case, and if it's a Dana axle, there will be a locking yoke actuator motor on one of the intermediary shafts. (Speaking from the viewpoint of a Dodge owner, it is located under the driver's side of the truck, half-way in between the knuckle and the front differential housing) Remove the wire for the indicator switch, then remove the vacuum line(s). If there is more than one, label one of them and mark which side it was on the vacuum actuator. The disconnect housing should then have 4 bolts that can be removed. Carefully lift the actuator out of the housing, there will be a fork that moves a locking collar back and forth on a splined shaft that's split in the middle. See if there is any oil left in there. If it's gunky, it can be siphoned or vacuumed out. Make sure that it is lubricated properly, and inspect the vacuum motor's shaft seal (o-ring) to make sure that it is intact and clean. You may have to rebuild the cork seal that keeps this happy and safe, but a bead of Permatex silicone will work well here. However, while it is open - lubricate the splines, fork, and collar with your finger and gear oil - I say this, because you can feel if there is any grit or broken splines. (The slippery oil will marginally protect your finger from snagging on something sharp) Once re-assembled and sealed - unscrew the actuator position switch and fill the hole with about 5 ounces of GL5 80w-95 gear lubricant. Screw the switch back in snugly, and then re-attach it's wire harness and the vacuum motor lines.

Ummmmm, the only other thing that comes to mind is that if you do not find a yoke on one side of the front diffy, the locking mechanism may be contained inside. If this is the case, check for fluid level and condition. You may have no benefit of a fill/drain plug there so prepare to get messy and drop the cover on it. If it's dry, that may be your problem. Worse yet, it's filled - but not with oil....I have seen clear water run out of differentials before; or this thick, tar-like substance that was once-upon-a-time hypoid gear lube. *laugh*

I am afraid I just do not know much on the full-sized Blazers. Jeeps, Subaru, Isuzu (Rodeo), Dodge Pickups - 80's style A-frame GM and my current Blazer is all I know about from the experience of ownership and maintaining.