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I recently purchased a 2005 Trailblazer LS with 158k miles. I get a continuous "thumping" rotational sound, similar to a flat spot in a tire, when I turn hard to the left. The best way to replicate the sound is to suddenly maneuver hard to the left. The sound will continue until I straighten out the wheel. Speed doesn't seem to matter although the frequency of the thump increases with speed. It sounds hollow and is loud enough to hear with the windows up or down. I do not feel it in the steering wheel or floor pans; the truck doesn't jerk, shimmy or shake.

Turning from a stop or low speed doesn't seem to trigger the noise.

It sounds like it is coming from inside the driver's side wheel well... it's somewhere between the hub and differential.

This truck had the hub assemblies and CV shafts changed just before I purchased it; now that I think about it, they must have been chasing this issue. Anyway, I checked over the hub assemblies, CV shaft outer nuts, and brake calipers to ensure they were torqued on both sides.

I drained the front differential fluid - it only had a hair over half a quart in it and was a little milky looking but nothing out of the ordinary for the mileage. Fluid didn't have an unreasonable amount of metallic glitter or any metal chunks in it. I filled it with about 1.5 quarts of 75w90 synthetic.

Front end feels nice and tight. No slop in the wheels with them jacked up. Ball joints, tie rods and sway bar links are good. The CV shafts don't seem to bind or have excessive slop - they wobble slightly at the differential and actuator if you grab them and shake them up and down (actuator side wobbles a little more). 4WD works perfect.
 

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I recently purchased a 2005 Trailblazer LS with 158k miles. I get a continuous "thumping" rotational sound, similar to a flat spot in a tire, when I turn hard to the left. The best way to replicate the sound is to suddenly maneuver hard to the left. The sound will continue until I straighten out the wheel. Speed doesn't seem to matter although the frequency of the thump increases with speed. It sounds hollow and is loud enough to hear with the windows up or down. I do not feel it in the steering wheel or floor pans; the truck doesn't jerk, shimmy or shake.

Turning from a stop or low speed doesn't seem to trigger the noise.

It sounds like it is coming from inside the driver's side wheel well... it's somewhere between the hub and differential.

This truck had the hub assemblies and CV shafts changed just before I purchased it; now that I think about it, they must have been chasing this issue. Anyway, I checked over the hub assemblies, CV shaft outer nuts, and brake calipers to ensure they were torqued on both sides.

I drained the front differential fluid - it only had a hair over half a quart in it and was a little milky looking but nothing out of the ordinary for the mileage. Fluid didn't have an unreasonable amount of metallic glitter or any metal chunks in it. I filled it with about 1.5 quarts of 75w90 synthetic.

Front end feels nice and tight. No slop in the wheels with them jacked up. Ball joints, tie rods and sway bar links are good. The CV shafts don't seem to bind or have excessive slop - they wobble slightly at the differential and actuator if you grab them and shake them up and down (actuator side wobbles a little more). 4WD works perfect.
Rotate the tires and see if it goes away.
 

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Discussion Starter #3
I'll have to try that tomorrow. I would think a tire issue would be continous and not isolated to turning in one direction but it doesn't hurt to eliminate as an issue.
 

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2008 gmc envoy_sle
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If all else is good.

check the front brake dust shields.

i had a similar issue, shields were rotted and broken and bent. see if shield is scraping the hub.
 

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I'll have to try that tomorrow. I would think a tire issue would be continous and not isolated to turning in one direction but it doesn't hurt to eliminate as an issue.
I know, but you said you didn't see anything obvious, so I'd rotate the tires. It's easy and like you say, eliminates one thing. Good luck.
 

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Discussion Starter #6
It doesn't sound like a dust shield where its metal on metal scraping. I'm going to switch around the tires, CV shafts and hub assemblies to see if the sound switches sides - if not, I think I can safely say this is an issue between the differential, intermediate shaft or actuator.
 

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2003 chevy trailblazer_lt_ext
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Have you checked your front wheel bearings ? Sounds like you have a bad one on the right front
 

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Discussion Starter #8
It doesn't sound like a wheel bearing. I truthfully think it's an issue in the front differential but I'll be switching the CV shafts, hub assemblies and tires around tomorrow to see if the problem switches sides. Otherwise it is an issue in the differential/intermediate shaft/actuator housing.

Disappointed if that's the case but the truck is in fantastic shape for a 14 year old northern state truck. The frame still has all of the original paint on it!
 

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Ok, makes sense. I re-read your post and I guess I misjudged the noise.
Sounds like its a pretty good thump noise. Odd that it only starts when you turn sharp Left but not when you start off slowly with sharp turn.
Almost like front axle not disengaged ?
I assume you have had the wheel apart and checked that all attachments are torqued down? Axle nut tight ?
Hope you solve it without too much of the green stuff needed
 

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Discussion Starter #10
Everything that the previous owner recently changed has been checked over. Driver's side hub assembly was not torqued down but wasn't loose enough to move around nor did it show any signs of doing that. Although I am very mechanically inclined (my roots are street/strip f-bodies, 1988-2007 GM full size trucks 1st generation SBC/BBC, 2nd generation SBC and 3rd generation LS motors), I am new to this differential setup and motor. I rebuild everything myself except for front differentials, transmissions and transfer cases. I have rebuilt two older 3 speed TH350/TH400 GM transmissions but I have yet to touch anything electronically controlled and I have never had a reason to rebuild a transfer case although I am confident that I could.

When I looked at this truck and saw the front differential, I was uncomfortable with the design. I bought this truck for my wife to drive while I do the second major overhaul on her 7.5" lifted 2002 Z71 Tahoe (new body mounts, a 2" body lift, wire wheel/paint the frame again, inner & outer rocker panels and replace the tired old 5.3 with a freshly rebuilt/cammed 6.0 LQ4) that I have owned since I was a kid and just can't part with after spending 100's of hours rebuilding and repairing. 🙃

The mechanic at work thinks it is the bearings in the actuator and we are hearing the intermediate shaft echo in the pan. I checked another Trailblazer and my passenger CV shaft has a little more wobble at the inner cup (which would point to the outer bearing on the actuator having some play so he might be right that the inner bearing is toast; his speculation is since it was an older man that he drove around in auto 4WD). I am not sold on his theory and think the differential or the bearings leading to the intermediate shaft are the cause since, in theory, the entire differential and intermediate shaft have to spin since the actuator is on the opposite side of the pan.
 

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Sounds like you have done your homework....time to get the wrenches out !
 

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Sounds like you have done your homework....time to get the wrenches out !
Simple enough to lay under the truck and see how it works. I am cringing at the idea of having to remove that front differential though because I can barely even reach it. I think I'll just pay the mechanic at work to do it if switching the tires/hubs/CV shafts doesn't relocate the issue to the passenger side lol.

I might even crack open the actuator housing while I am there to take a peak just to make sure it is the differential.
 

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Discussion Starter #13 (Edited)
Mechanic at work switched hubs and tires... noise was still present.
Mechanic removed brake caliper on drivers side... noise still present.
Mechanic removed drivers side CV shaft... noise still present.

Mechanic scratched his head, laid on the ground and noticed the tiniest mark in all of the wheel weights in the front end (since we switched tires). Removed weights, test drove and it was gone. We filed the weights down and problem solved.

Neither of us have an explanation as to why this would continously rub on the steering knuckle on a hard left turn only (you would imagine that the body would roll back at some point and stop making noise; but the geometry between the knuckle and tire shouldn't even be impacted by this).
 

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2002 chevy trailblazer_lt
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Were they thicker than normal wheel weights? Checked your ball joints lately?
Edit: reread this thread and saw "ball joints good". Tested how?
 

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Discussion Starter #15
Were they thicker than normal wheel weights? Checked your ball joints lately?
Edit: reread this thread and saw "ball joints good". Tested how?
Upper and lower ball joints were visually inspected and checked with a pry bar when the front end was jacked up. Their is zero play in anything in the front end.
Upper driver's side was also checked when the steering knuckle was broken from the UCA.

Regardless, it isn't a ball joint issue. The steering knuckle resides between the upper and lower control arms. The hub assembly is bolted to the steering knuckle; therefore the wheel and steering knuckle would never alter distances even if the ball joints were bad (if the upper or lower ball joint had slop, the steering knuckle and wheel would move as one). Nothing can really alter that geometry between the knuckle and wheel - so in theory this should have rubbed with every rotation of the wheel regardless or turning or going straight.

Perhaps both brand new hub assemblies (since nothing changed when they were reversed) have some run out when enough force is applied against them but I would imagine that you'd feel that level of run out in the steering wheel as a vibration.
 

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I operate stamping presses at work. One of my coworkers was having an issue with his press making a 'clink' noise at every stroke. He had maintenance over there looking at it. I happened to notice an unused manual clamp laying in the oil run-off tray that goes around the perimeter of that press. I reached down and picked it up. I told him to try cycling the press. He did, and the noise was gone.
He spent nearly an hour trying to fix that problem.
 

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I have a 2006 Envoy with a similar problem that sounds like a rubbing on the passenger side when turning right. Because my previous was a 2004TB that had the front diff bearings go because the inner UJ gave up (or vice-versa), and before i took everything apart to look for it, I bought new hubs and drive shafts just in case. Reading the above comments, I will look at the brake shield and balance weights, but maybe, seeing as I have the parts, can't hurt to change them anyhow. Just love this vehicle
 

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Discussion Starter #18
I have a 2006 Envoy with a similar problem that sounds like a rubbing on the passenger side when turning right. Because my previous was a 2004TB that had the front diff bearings go because the inner UJ gave up (or vice-versa), and before i took everything apart to look for it, I bought new hubs and drive shafts just in case. Reading the above comments, I will look at the brake shield and balance weights, but maybe, seeing as I have the parts, can't hurt to change them anyhow. Just love this vehicle
Check your actuator (where the passenger CV shaft meets the oil pan) for play up and down.
 

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Yes,,,my balljoint comment was more of a stab in the dark If my TrailBlazer wasn't 1500 miles away I would go out and look first! But clearly, SOMETHING is moving/shifting and there's not a lot in the area for it to rub on.

F-bodies eh? I had an 82, a factory ordered 86, and an 87 Trans Am. They were fun
 

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Yes,,,my balljoint comment was more of a stab in the dark If my TrailBlazer wasn't 1500 miles away I would go out and look first! But clearly, SOMETHING is moving/shifting and there's not a lot in the area for it to rub on.

F-bodies eh? I had an 82, a factory ordered 86, and an 87 Trans Am. They were fun
Yup, big f-body fan. More of a Camaro guy from 85-97 but the 98-02 WS6 Trans Am holds a very special place in my heart. I did have a 85 GTA with a mild 350/cam/5 speed 10 years or so back though.

I think this issue is due to poor wheel bearings in the new hubs. The force of a hard turn must make the bearing "walk/wobble" but I can't feel it in the steering wheel. Either way, I am not too concerned about it until failure symptoms are present.

These are good little trucks overall. Much better quality than the old Blazers!
 
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