Clunk in back end --Need serious analysis (not random guesses)
Thread Starter
Burning Brakes
Joined: Jun 2022
Posts: 845
Likes: 212
From: Florida
Clunk in back end --Need serious analysis (not random guesses)
Team,
I have been battling thing clunk/thud for about 10 months now, and I still can't figure it out.
- It's a clunk and/or thud...as if something is shifting or moving. I can actually feel it hitting.
- It only happens when I "enthusiastically" take off from a stop. Hold RPMs up to 1.5K or so, slip the clutch out some and then fully release. I'm not dumping the clutch at all
- It DOES NOT do the sound when backing up, going on an inclined driveway, going over a speed bump, hitting a pothole or expansion join. It only makes the sound when taking off.
I have replaced:
In my opinion, the mechanics of suspension flex and or movement is causing this. I feel like something in the suspension either has a worn bushing (batwing maybe?) or is lose (camber rod brackets bolts/nuts)
What am I missing? What haven't I checked?
Thank you,
Ric
I have been battling thing clunk/thud for about 10 months now, and I still can't figure it out.
- It's a clunk and/or thud...as if something is shifting or moving. I can actually feel it hitting.
- It only happens when I "enthusiastically" take off from a stop. Hold RPMs up to 1.5K or so, slip the clutch out some and then fully release. I'm not dumping the clutch at all
- It DOES NOT do the sound when backing up, going on an inclined driveway, going over a speed bump, hitting a pothole or expansion join. It only makes the sound when taking off.
I have replaced:
- All u-joints (main shaft/half shafts)
- both sway arms end link bushings (main bushings look ok)
- All wheel hubs (front and back)
- Dog bones bushings
- C- beam (went 5-10 lbs. over spec front and back)
- Rear leaf spring holding bolts (the ones on the diff...they were tight regardless)
- All bolts/nuts associated with removing both rear knuckles (torqued to spec after installing new hubs)
- Fuel tank is not moving
- EVAP canister is not moving
- Visual inspection did not reveal anything
In my opinion, the mechanics of suspension flex and or movement is causing this. I feel like something in the suspension either has a worn bushing (batwing maybe?) or is lose (camber rod brackets bolts/nuts)
What am I missing? What haven't I checked?
Thank you,
Ric
Last edited by rremesal; Sep 28, 2024 at 04:57 PM.
Thread Starter
Burning Brakes
Joined: Jun 2022
Posts: 845
Likes: 212
From: Florida
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
Even though you have tightened down the torque tube, there is a certain distance it has to be from the ( can’t remember if it was frame or floorboard? Anyway, it could be twisting just enough to make contact, thus the noise. Check repair manual for that measurement
Thread Starter
Burning Brakes
Joined: Jun 2022
Posts: 845
Likes: 212
From: Florida
Thanks for the tip.
Edit: BTW, I'm sure you meant the C-Beam or torque arm.
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Thread Starter
Burning Brakes
Joined: Jun 2022
Posts: 845
Likes: 212
From: Florida
I got under the car last Friday, and one of the things I checked was exhaust system movement. Other than slight movement back-and-forth at the rear hangers (under the rear bumper), there is no issue I can see. The slight movement is perfectly normal as the hanger is built to "slide" on its rubber holder.
Thank you.
Thank you.
Melting Slicks
Joined: Aug 2003
Posts: 3,407
Likes: 400
From: Lakeville MI
Try rolling the car backwards in neutral slowly and stabbing the brakes hard. Maybe take a video to see the wheel movement relative to the body. This should isolate the knuckle and dogbones from the drivetrain.
Thread Starter
Burning Brakes
Joined: Jun 2022
Posts: 845
Likes: 212
From: Florida
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
Melting Slicks
Joined: May 2014
Posts: 2,897
Likes: 592
From: New Port Richey FL
Probably already hit but the things that I have found to make that kind of noise is the C beam (Hit Hit again so out of loop) and the sway bar and ends being not seated in bar. They may be tight but tight enough. Also same with Shock Absorbers.
One Last afterthought, You Don't have a Forgotten Beer can or Lock Lug Key rolling around the Behind seat storage
One Last afterthought, You Don't have a Forgotten Beer can or Lock Lug Key rolling around the Behind seat storage
Last edited by s carter; Oct 1, 2024 at 08:11 AM.
Melting Slicks
Joined: Mar 2002
Posts: 2,882
Likes: 766
From: Sligo PA
By your description I had the same noise. It drove me nuts. It seemed it's loudest if I was beating on it and the trans shifted from first to second. I finally found out that the top of the C beam was hitting the fiberglass tunnel under the car. It hit so hard that it broke a small hole through. BUT before you think this is your problem understand that my car is 4L80e swapped with a fabbed C beam adapter. So my geometry is different than yours. But it might be worth a look just to see if there are any impact marks above the C beam near the transmission tail housing.
Thread Starter
Burning Brakes
Joined: Jun 2022
Posts: 845
Likes: 212
From: Florida
What year is the car? Are you in NE Florida by chance?
If does it when turning? Clutches in positraction.
By your description I had the same noise. It drove me nuts. It seemed it's loudest if I was beating on it and the trans shifted from first to second. I finally found out that the top of the C beam was hitting the fiberglass tunnel under the car. It hit so hard that it broke a small hole through. BUT before you think this is your problem understand that my car is 4L80e swapped with a fabbed C beam adapter. So my geometry is different than yours. But it might be worth a look just to see if there are any impact marks above the C beam near the transmission tail housing.
Probably already hit but the things that I have found to make that kind of noise is the C beam (Hit Hit again so out of loop) and the sway bar and ends being not seated in bar. They may be tight but tight enough. Also same with Shock Absorbers.
One Last afterthought, You Don't have a Forgotten Beer can or Lock Lug Key rolling around the Behind seat storage
One Last afterthought, You Don't have a Forgotten Beer can or Lock Lug Key rolling around the Behind seat storage
Thank you all for the suggestions...I really appreciate it.
Ric
EDIT: BTW, s carter...I like my beer from bottles. Keeps the product cooler, longer in my opinion. Also, I "try" not to drink when I'm under the car. Sometimes I succeed...sometimes I fail.
Last edited by rremesal; Oct 1, 2024 at 09:57 AM.