Rust Bust
Q I've been trying to remove the stub shafts from my Dana 30's Unitbearing with no luck. What's the trick?
A Even down here in the southwest were it never snows and hardly ever rains, separating the stub shaft from a Dana 30 Unitbearing can be a chore. The problem is compounded by the fact that in order to prevent vibration, the shaft's splines engage into the unit bearing with a rather tight press fit. Throw in years of rust and corrosion and you'd better be prepared for a fight when trying to dismantle some of these assemblies.
Your best method will involve a lot of time, patience, and penetrating lube. There are a lot of good ones out there, but you'll have to get a bit more serious than WD-40. We've had excellent results using Justice Brothers JB-80 (justicebrothers.com) and Federal Process Corporation's Free All (federalprocess.com).
Soak the nut and the shaft splines before starting. You may need to go as long as a week, reapplying the lube once or twice per day. If the nut hasn't rusted away, an impact gun will be your best bet for freeing the nut. Otherwise, go for a long breaker bar and give it hell. If the edges of the nut have rusted away, you could try a pair of channel locks or even Vise Grip pliers, but don't hold out hope for either working. Chances are you'll be carefully MIG or TIG welding a new nut onto the stripped, rounded one.
Once you get the nut off, either use an air hammer with a blunt bit to free the stub shaft from the unit bearing or thread the shaft nut back on a few turns to protect the stub shaft threads and whack away with a heavy dead-blow hammer. Resist the urge to use a steel sledge, as it will likely result in serious shaft, bearing, or hub damage. And don't break out the torch. Aside from the fact all that penetrating lube will go up like a Roman candle, you'll probably waste the bearing's grease and seals.
Death Wobble
Q I recently put larger tires on my Jeep and now I've got serious death wobble on the street.
A When trying to diagnose death wobble, always start small and work your way up. Although the larger tires may seem like the cause of the problem, in reality they are often only making an already existing problem noticeable. Start by checking the front wheel bearings. Simply jack the front tires up off the ground and, grabbing the top and bottom of the tire tread, try to wiggle the tire/rim back and forth. If any lateral play is noticed, check to see where it's coming from. The usual suspects are the hub bearing preload (or the Unitbearings on newer Jeep vehicles) or the ball joints.
If the hub adjustment, bearings, and ball joints check out okay, move on to the tires, making sure they're properly balanced. You can try mounting the rear tires on the front and see if that helps. If not, take the tires back to the shop that did the balancing and have them make sure the balance is still true.
With the tires ruled out, move on to the steering linkage tie rods and/or rod ends. Check the tie rod ends, drag link ends, and the track bar bushings (if applicable), as any one or combination of these can contribute to death wobble.
Finally, if your Jeep has been lifted, check the front axle caster. You generally want 4-6 degrees positive caster (bottom ball joint in front of top). Usually when a lift is installed the front axle may be rotated upwards to alleviate pinion angle and reduce driveshaft vibration. However, when the pinion is raised, caster is lowered. If your caster is too low, remove or replace the spring shims if your Jeep has leaf springs, or adjust the control arm length or (if applicable) the eccentric bolts to increase caster to the desired amount.