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Couple more issues with 98 Yukon

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I don’t know if you all remember me or not. About a month ago I posted about my Yukon misfiring terribly. I fixed that thanks to your expertise and now I have a couple other small issues. 


Number 1. I keep getting a P0430 code. I’m pretty sure the right side cat is bad. When reading the O2 sensors. The graph shows identical readings for the upstream and downstream sensors. I’m pretty much resigned to the idea that I’ll have to replace the cats, and found a new set for a decent price. Still I was wondering if any of you could recommend a good set. I can’t weld, so I’ll need to buy the whole assembly. I (think I) have some time on this because I don’t need another emissions test for over a year, but correct me if I’m wrong and if this problem is actually more urgent than I think it is.  


Second, and more importantly, I’ve got a squeaky wheel. I tried to diagnose it, by jacking each wheel off the ground and turning it manually, but nothing happened. I checked the CV joints and brake pads in the front, but after a really bad experience when I was younger I won’t mess with drum brakes, so I don’t know if something is up with one of the rear drums, and the rear axle doesn’t have CV joints. The noise seems to come from the front driver’s side wheel. So, if the CV joints and brakes seem fine does that mean the bearings are going bad? Is replacing them possible without an impact wrench and a hydraulic press? Could I just pack them and hope for the best? I’m going to do a little more trouble shooting and update the thread with any new pertinent info.





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I recently had the P0430 code.  Because I'm at 191k miles and still on the original O2 sensors, I went ahead and changed them out.  But, before I did, I found a very large exhaust leak where the cat Y-pipe bolts to the flange at the head of the tailpipe.  The flange is between the upstream and downstream O2 sensors.  I replaced the gasket and the O2 sensors and reset the code.  It's been 4 months and I've not seen that code again.  Either the leak or bad sensors (or both) can set the code, although I've always been told that 99% of the time the cats are bad.


The front bearings are part of a non-serviceable hub.  The usual indicator that they are going bad is having the ABS activate at low speed just before you come to a stop.  They usually don't squeak when bad, but rather make a grinding noise.  You can remove the wheel, caliper and rotor, then the big nut in the middle.  After that I think there's just 3 bolts attaching the hub.  No impact driver needed.  Remove the hub and grab the bearing.  Move it around and look for any play.  It should be tight and just spin.  If it's bad you'll need to replace the hub assembly.

You didn't say if the squeak is only during braking or not, or if it sounds like it's rotational.  In the front, the likely culprit are the brake pads.  If they're worn, the metal howler will make contact with the rotor and make all kinds of noise.  Or, the pads are producing harmonics and need to have anti-squeak stuff applied to them to make it stop.  There could be other causes but those are the most usual and most obvious.  In the rear, worn shoes can expose the rivets causing them to make contact with the drum.  Sometimes other components come loose and make contact with something they're not supposed to touch.  Pull the drum and make a visual inspection.

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