strange vibration in cab

gmbellew · December 28, 2005

the vehicle is a 2004 z71 suburban, 5.3L with 3.73, ~30,XXX miles. here is what i am going to tell the dealer when i get a chance to take it in:

2. Vibration can be felt inside the cab around 700-800 RPMs. Noticeable when engine is cold and transmission is in gear. Vibration decreases as operating temperature and/or outside temperature increase.

a. Best way to observe vibration is on first engine start up of the day, when it is below 32 degrees outside. Put transmission in gear immediately after starting, and the engine will idle around 700-800 RPMs. The vibration is prominent in this case. If transmission is moved to N or P, vibration stops, even when the RPM's remain the same.

b. It can also be observed when engine is warmed up, but the outside temperature is still below ~40 degrees. If place vehicle in D, with foot firmly on brake, depress gas pedal just enough to bring RPMs to 700-800, the vibration can be felt, but to a lesser extent.

c. Once outside temperature is above ~40 degrees, vibration cannot be felt.

it doesn't seem to idle any rougher when the vibration occurs, and i just had my throttle body cleaned. not sure if it is an exhaust resonance issue, driveline vibration, or some kind of vibration coming from the engine.

any thoughts?

thanks.

pm26 · December 28, 2005

Engine mounts?

gmbellew · January 5, 2006

ttt

gmbellew · January 11, 2006

i am getting ready to head back to the dealer, and wondered if anybody had some ideas on what the culprit may be. i like to be informed when i go in.

tbone69 · February 1, 2006

i am getting ready to head back to the dealer, and wondered if anybody had some ideas on what the culprit may be. i like to be informed when i go in.

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Did you find anything out from the dealer? I have the same problem.

XR Man · February 1, 2006

I have the same problem--not really a rough idle, it is a vibration/resonance. Let us know what you find!

gmbellew · February 1, 2006

I have the same problem--not really a rough idle, it is a vibration/resonance. Let us know what you find!

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sorry guys. it has been unseasonably warm here, and i haven't taken it in yet. i am waiting until it gets really cold (that is when teh vibration is the worst) so the dealer can't tell me that they don't notice it. it is supposed to turn colder here next week, so i will start looking to take it in soon. i will post an update when i find something out.

XR Man · February 11, 2006

I tore my dash apart some looking for my resonance and think I got it. I think it is the damper that controls the amount (not direction) for the HVAC vent on the driver's left side. I am going to try sticking some anti vibe pieces normally used on compund bows on it and see if it fixes it. I am also spraying a rubberized coating on the tiny tab that connects the damper to the vent. I hope that works. Ideally I would remove the damper and put very thin washers on either side of the shaft it pivots on but I cant get it out. I am aslo stuffing closed cell foam alot of other places while I am in there to quiet other rattles/possible sources of the resonance.

caremd99 · February 12, 2006

I have the same problem--not really a rough idle, it is a vibration/resonance. Let us know what you find!

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I have the same problem too. It didn't do this last winter during the cold so I am not sure what changed this year.

gmbellew · February 21, 2006

i took it into the dealer. they updated my computer with something that was out of date. it didn't fix the problem. guess i will take it back again, when i get time.

i wonder if it is some sort of exhause resonance, and once things get warm, it gets better? thoughts?

anybody else figure out anything?

XR Man · February 22, 2006

I thought it was the damper but it isn't. I d**n near have the whole dash out with no luck

jsbossert · February 23, 2006

I have it too, heard rumors of cats, O2 sensors, even timing chains. I have no clue, doesnt seem to affect performance though! Let me know what you find.

jsbossert · February 23, 2006

was just out probing, it seems there are alot of heat sheilds from manifolds back, i really believe its a vibration with them, you know how metal can make some weird noises in various situations.

gmbellew · March 6, 2006

finally got a solution to my vibration problem. i can't even notice it anymore.

apparently it was the exhaust system causing the vibration. here is what the work order says -

B cust states they are feeling vibration inside truck around 800 rpms. most noticeable when eng is cold and trans is in ear. decreases as eng temp rises.

Cause: Harmonic vibration in exhaust

L2020 Hanger and/opr clamp, exhaust system replace.

4 10199232 Dampner A

2 NNPNN Clamp

Perform bulletin PIP3121D Installed 4 weights to exhaust system per bulletin.