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H3 Clunk noise when decelerating

awalsh

awalsh

Well-Known Member
Messages
349
Location
New Jersey
I wouldn't post this unless I truly had no idea what this noise is but here we go..
Trucks been fine (no noises, etc) for a while after I did a new rear u joint in January..
Spilled water on my headunit and messed it up a bit so sometimes I don't have music at all
Because of this, the other day I noticed this weird popping/clunking noise whenever I decelerate almost to a stop - braking or just coasting to a stop
Sounded like it was coming from under my feet so sure enough I realized one of my skid plates (one under the dif) had a broken bolt and was dangling so I took the whole thing off
Thought I solved the problem but sure enough same noise came back today
It's hard to really pin point since I can only hear it when I'm decelerating
So what I do know to rule some things out.. It's not the u joints all are in decent shape, not the crossmember bushing, not a skid plate or heat shield
What it could be.. Maybe something in the rear brakes but not too familiar with brake noises, or maybe a hub? Also my front shocks are blown and squeak but I don't think that decelerating would cause for a weird clunking noise
I'll post a video if that helps but I just wanna fix this damn thing it's making me go nuts


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RamRod

RamRod

Well-Known Member
Messages
3,914
Location
AB, Canada
I would check the three bushings on the front axel - sounds to me it is "wrapping" when the brakes are applied then getting released *clunk* once the brakes are being let off.

Check the cross member and the bushing near the halfshaft (on both sides) for any play
 
awalsh

awalsh

Well-Known Member
Messages
349
Location
New Jersey
RamRod said:
I would check the three bushings on the front axel - sounds to me it is "wrapping" when the brakes are applied then getting released *clunk* once the brakes are being let off.

Check the cross member and the bushing near the halfshaft (on both sides) for any play
Click to expand...

Will do on both of those but it's like a chatter not even a clunk
I swear I'm going crazy.. I haven't washed the undercarriage in a month and have been through some mud, used a pressure washer in the rear brakes and poof it's gone.. Still not satisfied there's no way it was because of a tad bit of mud.


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alrock

alrock

El Diablo
Staff member
Messages
10,677
Location
Scottsdale
Exhaust could be hitting the crossmember. Broken motor mounts could be allowing engine to rock. But I'd look at exhaust first. Or a loose caliper.
 
awalsh

awalsh

Well-Known Member
Messages
349
Location
New Jersey
alrock said:
Exhaust could be hitting the crossmember. Broken motor mounts could be allowing engine to rock. But I'd look at exhaust first. Or a loose caliper.
Click to expand...

Checked exhaust/the crossmember seems in tact. Definitely not the motor mounts though just had new ones put in when I put in a new motor. Definitely will look at the loose caliper option though


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rascole

rascole

Well-Known Member
Messages
2,852
Location
Bellflower, CA
Double check the diff crossmember with a wrench. It may LOOK tight with the rubber and it only needs 1/2" to make a loud noise. I had the same issue, the diff was rotating up and down and hitting the crossmember before I installed the Scorpworks replacement. I used my GoPro on a magnetic base to search for noises when I drive and it's amazing what you will find with video.
 
awalsh

awalsh

Well-Known Member
Messages
349
Location
New Jersey
rascole said:
Double check the diff crossmember with a wrench. It may LOOK tight with the rubber and it only needs 1/2" to make a loud noise. I had the same issue, the diff was rotating up and down and hitting the crossmember before I installed the Scorpworks replacement. I used my GoPro on a magnetic base to search for noises when I drive and it's amazing what you will find with video.
Click to expand...

Good idea! I'll crank it down a bit anyway for safe measure, hoping that it's not anything else crossmember related because I'm 1000 miles from home and any sort of real tools


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4speedfunk

4speedfunk

Well-Known Member
Messages
4,250
Location
Tardville
Check the ENDS of the crossmember (not the bushing)...specifically where it bolts to the frame. They often crack here, and I have welded several of them. You will need to remove it...clean the ends with a wire brush...and look real close with good light. The mounting bolts are often loose, allowing the crossmember to rock back & forth, eventually creating stress cracks around the bolt holes. GM redesigned the part and sells it for $450 but, welding works good too. Scorpworks sells pre-welded reconditioned ones I think.
 
Last edited:
awalsh

awalsh

Well-Known Member
Messages
349
Location
New Jersey
Since this forum is already started.. What is the name of the bolt fastener for the skid plate (the ones on the 2nd skid under the crossmember) or does anyone have a link?


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awalsh

awalsh

Well-Known Member
Messages
349
Location
New Jersey
Bruces said:
Sounds more like front prop shaft cv joint to me.
Click to expand...

Could be.. But no noticeable grease or anything out of order. Also the noise has gone down drastically since I pressure washed everything from brakes to axles etc, anything moving which would cause a noise. Still need to torque down crossmember and check brakes but I planned on replacing the prop shaft cv anyway so that will be added to the list [emoji58]


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