front diff or wheel bearing? - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > 4x4 Drivetrain

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Old 12-19-2009, 08:05 PM
Grizzledbiker Grizzledbiker is offline
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2003 Chevy TrailBlazer LTZ
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Location: Grand Rapids, MI
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Question front diff or wheel bearing?

'03 LTZ. I need some help determining whether I have a drivers side front diff bearing or wheel bearing problem. Symptoms: classic 30mph whomp-whomp-whomp that sounds and sort of feels more like a wheel bearing. And gets a little worse daily. But, it doesn't change whatsover when turning right of left (checked it out into a big empty parking lot). The drivers side front diff bearing is suspect because of seal leakage plus a little play is felt there. I don't notice any play when grasping the tire/wheel up/down, side to side. Nor do I hear any noise when turning the wheel by hand either at the hub or the diff. As part of this investigation I drained the front diff oil and did not see any metal particles fall out although it was certainly old and a multi hue yucky brown. Pulled fill plug and was able to get a magnetic probe in there. Found some filings but nothing I would consider really significant. Re-filled new stuff and test drove it. Yep still goes whomp-whomp-whomp which is louder at 30mph. Now let me say there is no vibration at all. And in fact it is not all that noticeable at highway speeds. So what do you think guys? I'm tempted to go ahead and change the left hub assy regardless as it's readily available at AutoZone for $180 or so and certainly cheaper than front diff work. Also looks like something I could tackle ok on my own. Your input on this would be most appreciated.
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Old 12-20-2009, 10:15 AM
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markarock markarock is offline
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2006 Chevy TrailBlazer LT
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The driver's side bearing, unlike the passenger side, is lubricated by the differential fluid. So the odds of it going bad are pretty small in my opinion. Plus you found no evidence in the drained fluid or with a magnet of heavy wear.

The hub bearing assemblies are known wear items and go bad regularly. Plus, even though bad, you can seldom feel anything wrong when spinning it by hand.

So, I would agree that you should change the hub bearing first. That's what I'd do.

Just to be sure it is not a tire, I'd rotate them first to be sure it is not your left front tire.
3.73; G80; Bose; XM; DIC
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Old 12-20-2009, 10:41 AM
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Robert1101 Robert1101 is offline
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2003 Chevy TrailBlazer LS
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CV joint is another suspect. Any soft clicking sounds when you go in a slow circle either forward or reverse?
Earth first, we will strip mine the other planets later 3.73's, G80, 4X4, PCMforLess, Flowmaster 70, K&N 57
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Old 12-20-2009, 01:18 PM
Grizzledbiker Grizzledbiker is offline
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2003 Chevy TrailBlazer LTZ
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Location: Grand Rapids, MI
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negatory on the cv joint clicking on turns (had a bad one in '93 Dakota). But what about the inner cv joint? What are symptoms of that sucker going bad?

My gut feeling is that of the drivers side diff bearing is going bad, And that whomp-whomp-whomp is that of the axle shaft slapping up against what's left of the bearing. Pulling and examining the shaft would verify that. But I do agree I might as well change out the hub too. I've got some wrenchin' time available during christmas break though sub freezing temps out in the un-heated garage are certianly less than favorable.
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