QUESTION: I drive a 2005 GMC Yukon 4x4. I recently noticed my yellow brake warning light coming on. I jacked up the front of the truck, thinking I'd take a look at the brake linings. Just before removing the wheels I noticed the right front wheel was loose when I grabbed it and shook it compared to the left one. It moved in and out by a half-inch about where my hands were. I checked the lug nuts and they are tight. Where do I proceed from here? I parked it in the mean time.
ANSWER: Your message shot right to the top of my want-to-help-with list, as this is a dangerous situation. Based on the two symptoms you mentioned, it sounds like the Yukon's right front hub (wheel) bearing is beginning to come apart. Should a hub or wheel bearing become loose enough, it will often cause the ABS brake system wheel speed sensor, located within the bearing hub on the Yukon, to rub against the reluctor, the toothed surface of the hub. That can damage it, resulting in an illuminated warning light and diagnostic trouble code being set.
The good news is that modern wheel bearings are often consolidated into a bolt-on hub assembly, making replacement pretty simple. But the bad news is the parts cost is downright ugly. What used to be $25-$50 in parts and grease for individual bearings can reach $400 or so for the bolt-on hub assembly.
If you're a do-it-yourselfer, this job is pretty straightforward after removing the wheel, brake rotor, caliper, and caliper bracket. The only tough part is some very tight and large metric bolts (21 and 22mm, and axle nut (36mm), which require tools that are likely beyond the scope of the typical home tool box. The axle nut should also be renewed, as its self-locking capability cannot be trusted after removal and reinstallation. It's tightened to 177 pound-feet.
When shopping for parts, you may find bearing and hub assemblies for as low as $60 but I'd resist the temptation. Look for a respected name part such as AC Delco, SKF, Moog, Timken, Raybestos, or other recommended by a local parts house for about 2-4 times that. When it comes to parts that hold my wheels on or stop the truck, I steer clear of the cheap stuff.
NOTE: In a follow-up to the trunk emergency kit, several readers offered additional suggestions. A few thought I was nuts to carry so much dead weight around; it does depend on the trip if the "B" kit gets thrown on board. Here are some great additions — as space permits:
Will: 30 feet of rope
Mark and John: Lithium flashlight batteries, which last perhaps a decade
Neil: Prepaid phone and charger
William: Toilet paper, kneeling pad
John: Small axe or hatchet
Florence: Folding shovel, washer fluid, de-icer
Jerry: Nylon tow strap, forehead LED lamp
Hal: Tube of E-6000 sealer (available at craft stores; Hal says it works better than anything else he's seen), lightweight cigarette-lighter air compressor.
Blaine: Tire plug kit, which works better than sheet rock screws but requires tire deflation and reinflation
ABOUT THE WRITER
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at email@example.com; he cannot make personal replies.
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