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Vibration in Driveline

121 Views 7 Replies 3 Participants Last post by  Steve40th
93 C4, Okay, at 2500 rpm and at 4500 rpm I have a vibration under medium to heavy throttle. Does not matter if AC is on or not.
In neutral, or park, the problem is not there.
Had main drive shaft checked. Good, and balanced.
Half Shafts have zero movement, and as driveshaft, has spicer u joints. They are a few years old, but very few miles.
I replaced end links on rear sway bar. Rubber was gone.
Hal Shocks, no leaks.
DRM Long tube headers since 2001 era, and OEM cat back exhaust.
700R4/4L60 Pro Built Automatic with Vigilante 2800 stall
New tires.
Center beam has ZF Docs plates, and they are torque per FSM.
When you get on it, half or full it feels like something is vibrating/hitting the floor boards. Feels like exhaust is hitting. But, when I was under there, I cant see where the exhaust could be hitting. Maybe under torque, it is. Motor mounts are tight, I just did that a couple days ago.
So, thats all I can think of.
Thoughts, suggestions?
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Did you replace the motor mounts because of the vibration or did it start after you replaced them?
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I did not replace motor mounts. When I tried to replace them, I could not remove the passenger side due to headers. I looked it over, and the other one, and they were fine. No issues, no cracks etc.
I need to either look at the balancer too. Check it while running at revving it slowly to see if it looks bad. Physicall looking at it is fine. No cracks or separating.
Weird is it is at two different rpm spots.
Tested more.
Vibration in all gears same rpm.
Pushed brake to see iff TCC disengaged, it did.
Torque braked a bit at stop, and vibration is present.
Opened hood, went back and forth with reverese to drive. Engine Barely moved. Idles at 800rpm.
In nuetral nothing.
SOLVED. I have found the issue at hand. Left side/drivers OEM exhaust is/was touching in two spots on body. The shield was touching the body.
Also, the header triangle plate was touching ever so slightly.
Its not fixed, as I need to figure out what was wrong with the exhaust to touch. Is it bend ever so slightly upward?
The header collector clamp needs trimming..

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Glad you found it. Things like that will drive you absolutely bonker
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I’ll tare a car apart looking for a squeak. The issue your having would drive ma crazy.
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A C4 has so many squeaks, rattles etc. Stereo took care of most of that. Dynmat? took care of allot of the rest.
But, I this car is showing its age.. I have had it since 1996, and that has helped me out significantly as I know it pretty well..
But vibrations like this , uggh.. Now, I just need to permanently fix it.
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