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2002 chevy trailblazer_ltz
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3 Posts
Discussion Starter #1
First post, sorry if it is a repeat. I have been searching all morning, but haven't found anything fitting my scenario.

Mods, please feel free to move if this is the wrong place for this.

I just picked up a 2002 TB LTZ I6 2 days ago with 109K miles on it. I took it for a 30 mile county road ride this morning and heard a faint whine or hum coming from the rearend (I think). It only happens when holding the throttle steady or accelerating. Doesn't seem to be based on rpm, but it only happens above 50mph. It does change as speed increases or decreases. I, of course, have not tried it in 4x4 at these speeds. It switches into A4HI, 4HI, and 4LO just fine...even though I can barely tell it is changing.

In A4HI or 4HI, I can't hear any noise, but this is at slower speeds.

Fluid levels are good in transfer case and rear diff. Fluid seems good.

No other noises, no grinding, clunking, rattling, or shaking.

My next step would be to change all fluids, but I am looking for any ideas of what to look for.
 

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2005 gmc envoy_denali
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28 Posts
Check to see if there is a grease fitting on your U-joints. That would be the cheapest thing to replace first.
 

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2002 chevy trailblazer_ltz
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3 Posts
Discussion Starter #3
Thanks for the idea. Sometime in the next couple days I should be able to check that.

What about changing the fluids? I presume that would be another good thing to try.
 

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2002 gmc envoy_slt
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3,203 Posts
Might be tire noise as well. Try swapping them front to back to see if the hum changes or moves to the front.

At 109k, I'd definitely change the fluids, unless you know they've been done. The transfer case can make some noise if the fluid is done or non-autotrac fluid installed......btw, RP Synchromax meets autotrac specs.
 

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2002 chevy trailblazer_ltz
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3 Posts
Discussion Starter #5
Thanks for the tip. I don't know if the fluids have been changed recently which is why I was thinking of just doing it.

When I fist heard the noise, I thought it was tire hum or maybe a wheel bearing. but since the noise goes away completely when I let up on the throttle, it led me to believe it was something else. I could be wrong though.
 
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