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2004 chevy trailblazer_lt_ext
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Discussion Starter #1
I have a 04 TB EXT 4x4 that has developed a 'rattle' above 45 MPH. It is more of a vibration in the floorboard than a noise and is only noticeable on a smooth road. The best description I can give is it feels like someone is hitting the floorboard with a rubber mallet intermittently. The frequency does not seem to be consistent or linked to RPM/MPH. I blew a seal on the front diff a couple of years ago and had that replaced. I checked all the U-joints for play and they seem fine. The car has 161K and has been fantastic other than a few minor issues.
 

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2004 buick rainier
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109 Posts
Possibly a front hub assembly. See if one wheel feels hotter than the other, also try to see if it's louder on one side of the car than the other by having some one else drive.
 

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2004 gmc
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26,181 Posts
Or CV joint, or the bearing where the CV shaft fits into the front differential (driver's side) or the splined disconnect (passenger side).
 

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2004 chevy trailblazer_lt_ext
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Discussion Starter #4
I've got a mechanic looking at it right now. There is no sound just the feel through the floorboard. A friend said the front driveshaft only turns when in AWD or 4WD which would eliminate the front differential. Is that correct? I'll let you know what the mechanic finds for future reference. Thanks for the replies.
 

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2004 gmc
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26,181 Posts
It eliminates only the front driveshaft. The wheels are always connected to the CV shafts, so they spin all the time, even in 2HI mode. Actually, parts of the front differential are always spinning, even in 2HI mode. The only parts that aren't spinning are the pinion gear, ring gear and carrier.
 
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