Having the drivetrain of your daily driver vibrate can get annoying really fast.  Just ask my wife. She told me that she could hear a vibration at 25 mph and then she could FEEL the vibration really bad at 45 mph. She also told me that as she turns to the right really fast, the vibration goes away, but as soon as the wheels are straight, the vibration is back. Hmmmmmm, sounds like wheel bearings to me. 

I don't know how long wheel bearings are supposed to last, but after 140K miles and larger tires, I am sure it is time to inspect them. Well, that is not so easy on a Jeep Cherokee's Dana 30 front axle. The front wheel bearings are incorporated into a one piece hub assembly which takes special tools to take apart. For most of us, this hub assembly is a non-serviceable part. I took the easy way out and purchased a new hub assembly from the local auto parts store. 

Follow along as I show you easy it is to replace the wheel bearing assembly on a D30 front axle. 

	I began by setting the parking brake and blocking the rear wheels. Then I jacked up the front axle and set it on jack stands and removed the wheel. I removed the 2 screws holding on the caliper and suspended it so it was not hanging by the brake line. I removed the rotor (it just slides right off). I unwrapped the cotter pin, pulled it out and removed the axle shaft nut retainer.
	I was lazy and used a 36mm socket and my 1/2" impact wrench to remove the axle nut and washer. (If you don't have an impact wrench, you could try to have someone step on the brakes while you loosen the nut. Or you could keep one front tire on the ground, put the transfer case in 4 wheel drive and then loosen the nut with a breaker bar. )
	There are three bolts that hold the wheel bearing hub assembly to the steering knuckle. The heads on these have 12 points so you need to use a 12 point wrench to remove them. I used a 12 point, 13mm socket wrench to remove the 3 bolts.
	With a little luck the wheel bearing hub assembly should come right out of the steering knuckle. I was not that lucky and had to use a 3 jaw gear puller to remove the driver's side (the passenger's side just pulled right out).
	Here I am sliding the hub assembly off of the axle shaft. You can see that I did not completely remove the 3 bolts from the back side of the steering knuckle. I left them sticking out so the rotor dust shield would not fall off.
	Here is a picture of the used and new wheel bearing hub assembles.
	Since the splines of the axle shaft and the old hub assembly looked rusty, I coated the splines with some wheel bearing grease.
	I also coated the splines of the hub assembly and the back flange where it mounts into the steering knuckle with wheel bearing grease. Hopefully this will make it easier to remove if I ever have to take the front axle apart again.
	I applied some red Locktite to the threads of the 3 mounting bolts and tightened the hub assembly.  I torqued the 3 bolts to 75 ft.  lbs. Then I installed the axle shaft washer.
	I installed the axle shaft nut and torqued it down to 175 ft.  lbs. To do this, I had to put the passenger tire on the ground and the transfer case in 4 wheel drive to prevent the hub assembly from rotating.
	I reinstalled the axle shaft nut retainer (looks like a castle nut) and lined up the openings with the hole in the axle shaft. Then I installed a NEW cotter pin (2" x 3/16") and bent it to lock the axle nut retainer in place. Do NOT reuse cotter pins.
	I reinstalled the rotor onto the hub.
	I slipped the caliper back over the rotor and tightened up the 2 caliper mounting bolts.
	Reinstall the tire, torque the lug nuts and take it out for a test spin (remember to put the transfer case back into 2 wheel drive). And that is all there is to it.