Question: A buddy and I have a disagreement regarding how often one should repack front wheel bearings. He says that his Cherokee uses a wheel hub that comes factory-sealed and can't be repacked, and is good for, like, forever; therefore there is no reason to have to repack the wheel bearings on my Jeep that has locking hubs.
Jim Hoffman
Bend, OR
Answer: Well, your buddy is partly right. His Jeep Cherokee, as well as the rest of the pack of newer Jeep vehicles, uses a sealed unit bearing. While not "good forever," they do last a long time mainly due to the design of the seal and the fact that there is no locking mechanism that can allow water and dirt to enter, no matter how well the hub manufacturer tried to prevent it. On a vehicle with locking hubs, it is imperative that you periodically do check the wheel bearings.
Part of my yearly maintenance procedures on my trail Jeep is to repack the wheel bearings. OK, maybe it's a little excessive compared to the relatively low miles that are put on it each year, but I figure that it's just good insurance if nothing more than to check things out. It's a good thing I do this, as this year I discovered that a seal had leaked, water had intruded and, well, the wheel bearings were trash. Repacking them is not a pleasant chore, nor is adjusting the preload and locking the nuts in place, especially when you have to fight with either of two styles of retaining nuts. If you have the double-nut, bend-over flat washer style, then you know that you can only bend it over so many times before it breaks and has to be replaced. If your hub nuts are of the type that use the little locking pin that has to line up perfectly with the proper hole in the locking ring-plus the tab on the ring must fit properly into the slot in the spindle-you know what a pain that can be.
I came across a new interesting locking mechanism this last year from Stage 8 (800/843-7836, www.stage8.com). Yep, the same people who make the neat locking bolts. Instead of the locking pin that never seems to line up properly, the new XLock system uses specially designed components that make installation a lot easier than before. XLock is made from 4130 chromoly steel, through-hardened. Originally designed for the U.S. Military, the patented locking spindle nut has been modified to fit Dana 44 and Dana 60 front spindles. The engineer I spoke with at Stage 8 told me that the XLock will withstand 450 lb-ft of reverse torque without failing or loosening. No, that does not mean it will withstand 450 pounds of torque when the vehicle is backing up. It means that if the locking retainer is not removed, it would take in excess of 450 pounds of torque with a wrench to loosen or break the locking system.
I just happened to get one of the early prototypes to try out. And guess what? There was a design flaw. Not in the overall design, as that was great, but in the thickness of the grooved spindle nut. Seems that the Scout-style Dana 44 front hub/spindle combination that I was using is a bit different than those of the GM variety; the spindle nut was too thick and would not allow the Warn hubs that I was using to fit properly. I was able to machine the thickness down on the spindle nut so it worked as it was originally intended. As a result of my finding, Stage 8 has now incorporated a thinner-designed spindle nut in the kit.
How it all works is that first you install a thrust washer over the spindle against the wheel bearing. Next comes a washer that is notched on the outside and has a tang on the inside that follows the machined groove in the spindle a lot tighter that the original setup ever did. The spindle nut, besides having the notches for the hub wrench to fit into, also has a shallow groove around its circumference. Once the proper adjustment is made to the wheel bearings, you slide over the locking retainer so that it engages both the notches on the spindle nut and those of the notched washer behind it. A pair of pin-style snap-ring pliers work here for getting it into place. You have eight different positions that it could fit into, so rotate it around until it fully engages. Then install the large snap ring into the groove on the spindle nut to hold the locking retainer in place.
Oh, and you can buy them directly from Stage 8 if your friendly off-road shop doesn't have them.
Question: My Chevy pickup has ABS brakes that are acting strange. When I apply the brakes for a normal stop, the pedal kind of pulsates like it would if I was doing a panic stop. It only does this at slow speeds.
I took it to one shop where they replaced, I believe, something called a "dump valve," but it didn't make any difference. Another shop wants to replace the pump and ECM, both of which were quite expensive. Is this what I have to do to make my brakes right, or do I just live with the problem if it's not a safety issue?
Mary Peterson
Ann Arbor, MI
Answer: You failed to tell me the year of your truck, but I'm going to make an educated guess that it's a few years old, and another guess as to the cause of the problem is based on where you live. Michigan winters and road salt mean rust and corrosion.
At each front wheel is a thing called a speed sensor, which does just what its name implies. Actually, it's part of the front hub assembly. Without going into a lot of detail, here is how it works: A tone wheel inside the hub sends a signal to the speed sensor, which relays information to the ECM (electronic control module), which in turn sends a message to the ABS pump and its components to regulate brake pressure.
Now if the tone wheel fails to send the proper signal, then the total ABS doesn't work properly. My guess is that there is a corrosion buildup either on (or under) the pickup sensor that has changed the distance between the sensor and the tone wheel. Sounds like a minor problem, but the clearance here is quite important.
Have your shop remove the sensor and clean it thoroughly before reinstallation. While they're at it, have them use a scope to monitor the wheel speed sensor output where it is hooked up to the ECM connector. This way, any wiring or connector problems will also show up. When you show this to them and they just say, "Duh!," be sure to find another shop!