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Ok Guys,

I consider myself a reasonably competent mechanic, but this one has me stumped...hoping someone has some past experience that can shed some light.

My '94 has had a dull, rhythmic "rubbing" sound coming from somewhere in the front for about two years now.  It's noticeable even at low speeds (10MPH), and progresses into a noticeable vibration at 60+ that you can feel through the steering.  The noise is purely speed dependant, does not change if the car is accelerating, cruising, or coasting in neutral.  I always assumed it was a bad tire (the noise has a "dampened" sound, not sharp or metallic, and I noticed some slight bulging in the sidewalls of both my el-cheapo front tires).  It's never been more than an annoyance, so I just lived with it.

The car's at an age where front end work started becoming necessary (for other symptoms, not this noise).  Within the past two years, I have replaced both ball joints, both struts and mounts, both halfshafts, pads and rotors twice, and the LF wheel bearing twice (bought the Chinese one the first time, shame on me...).  Still, the noise remained.  Again, not causing enough of a problem for me to really care, and the fact that I replaced all these parts without any change seemed to support my conclusion that one of the tires was the cause.  Well, I finally tore up a tire, so I had both fronts replaced - to my astonishment, the noise got WORSE.  The pattern is the same, but now the low speed rumble is more pronounced (seems to resonate in the A-pillar trim) and the high-speed vibration is very noticeable, it feels like a loose wheel (obviously, I checked that).  My first theory is that it's the RIGHT side wheel bearing - it's pretty much the only  rotating part up there that hasn't been replaced recently (about 85k on it), and the noise seems to get ever so slightly worse on left turns.  I'm thinking the new tires have a stiffer, "knobbier" tread than the old, balding ones, which is transmitting more of the vibration back into the hub.  The thing that makes me wonder, though, is that I have had this same noise for about 2 YEARS (40,000 miles or so), and I've never heard of a wheel bearing that makes the same noise for that long (especially this particular hub bearing - they tend to just go into "full-grind" mode without warning).  I also don't notice any play in that wheel (or the other one, which I checked for reference), and I don't hear any noise eminating from it with the wheel jacked up and spinning (engine-driven at about 30MPH, not just a hand spin).  The mechanic that aligned my new tires didn't say anything about worn bearings, or any other worn parts that would keep the car from holding an alignment.

Has anyone ever seen a wheel bearing make noise like this, for that long, without exhibiting any more obvious defects?  Obviously, with that many miles on it, the thing to do at this point would be to just replace it anyway and see if it clears up - I guess I'm just looking for some hope that I'm not wasting money that I'm gonna need to tear apart the transaxle to replace carrier bearings or something...any thoughts?

You don't say if this is a manual or automatic.

If it is an automatic, there could also be some internal problems.

If a manual then there is a stub shaft on the passengers side that drives the right wheel.  This shaft has a carrier bearing in it on the far right side that could cause a shake.

If you can't find any play in the wheels with the car jacked up then I would start looking elsewhere.  I don't guess you have a really bad motor mount?

It's an automatic, and actually I have begun to notice what I assume is a little bit of converter shudder around 50 MPH, under light to moderate load (168k on this car, so it's not that surprising) - I don't think it's related though, this "mystery noise" is noticeable at very low speeds, and doesn't change if I take the care out of OD or let it coast in neutral.

The motor mount's an I idea I hadn't considered - would tend to rule it out though, because again, the noise doesn't change if I take it out of gear (at several speeds).  I'll see if I can get ahold of someone with a lift, I'm having a problem duplicating the nosie with the wheels off the ground (yet another reason why I was sure it was a tire), but maybe if I can get right under the driveline I'll be able to notice something.  Thanks for the reply!

Well, found out where the vibration is coming from...it's actually in the rear, I convinced myself that it was in the front because it seemed to be transmitting through the wheel, so I spent all my time up there...both rear tires are cupped on the inside edges, pretty bad on the driver's side but only slightly on the passenger's.  Problem is, I still have no indication of what caused it - both rear bearings are well below the runout limit in the GM service manual (checked them with a dial indicator), the trailing arm bushings are fine, shocks are pretty old (probably the factory originals!) but seem okay, no slop and they pass the jounce test...it's almost like the axle has "shifted" on the driver's side (which would induce a lesser shift on the passenger's side as well, explaining that wear), but I see no difference in wheelbase on the driver's and passengers sides (this was checked with a tape measure though, not exactly high precision)...probably a safe bet to change the shocks and mounts (as preventive maintenance if nothing else) with this mileage - 170k now...I'd just hate to wait until another set of tires gets chewed up to realize that wasn't the problem.  Anyone else run into this?  Checked the suspension forum already, no leads  

Since you've checked the axle bushings and the wheel bearings (did you actually grab the tire and try to move it around in addition to measuring runout?), there's not much more to suspect aside from wheel balance or some kind of bent component.  The solid axle pretty much rules out sagging springs/suspension or just a camber problem.  Your mechanic said nothing about your rear wheels needing to be aligned, huh?  If you haven't already, I'd swap the rear tires/wheels with the fronts and see if it changes anything...maybe there's a bent wheel.

Even Money on a bent rim, underinflated tires, or a bent component.  Could be the stab bar is tweaked, causing a tip in the wheel too.  Also the alignment should have been all wheels.

I had a simular problem on the front end of my GT.  it felt loose an wiggled when u turn left and sounded like a wheel bearing but everything was new except for the inner an outer tie rod.  well replaced them and no more  problems..

As for the rear ive seen where the gusset welds on the hub mounts bend in and wear the inside edge of the tire.
check everthing that everyone here comes up with!!

GM specs are allowing alot play in parts.  I fell that the specs should be a little tighter.


Mr Goodwrench