Odd problem - vibration at idle in 4wd ONLY

Maverickxeo

Original poster
Member
Jan 25, 2021
44
Alberta, Canada
I am trying to sort out this odd problem but I cannot find anything through searching. I should mention I come from Jeeps (and their very simple transfer cases and 4x4 systems, haha!).

In my 04 envoy, when I have it in A4WD or 4Hi, I will occasionally get a slight shake coming from what I believe is the transfer case. It does NOT seem noticable while driving, only when sitting (whether in drive or park). I noticed today that in 4hi, I had a bit of a 'clunk' while driving through an intersection twice - the same one. It did not 'slip' or have wheelspin, only a clunk presented itself. I then pulled into a parking lot shortly after, and it was vibrating. I put the transfer case into 2hi, and the same clunk presented itself and the vibration stopped.

Am I wrong to assume this is a transfer case motor problem? It seems to shift okay between all four modes (2hi, 4awd, 4hi, 4lo) in that I can hear the actuator engage and I did verify that the transfer case is in each of these modes once selected (up in air on jack stands).

As a side note - I only use 4hi when the roads warrant it - for example, today the roads were covered in snow and ice.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Are you switching to 4hi on solid asphalt? You might be experiencing crow hop. You need some wheel slip to allow speed differences between the front and rear wheels. However, in A4WD, you shouldn't be feeling anything unless the rear wheel slip and the front wheels are engaged by the transfer case.

Maybe your front U-joints are failing?

Check the FAQ for links to transfer case operation and troubleshooting. Link in my signature.
 
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Maverickxeo

Original poster
Member
Jan 25, 2021
44
Alberta, Canada
I was engaging 4x4 on the snowy/icy surfaces. I dont think it would be u joints just because of the idle vibration unless its a secondary problem. I know I checked u joints a while back and they felt tight.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Idle vibration is likely the engine mounts. Maybe the added torque or something from the 4x4 engaged is making the vibrations more evident from marginal mounts.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Maybe. Could just be the fact that there's more stuff "connected" to send the vibrations. If they're original and high mileage, I'd replace them. Get only ACDelco mounts as aftermarket don't dampen well.
 

Maverickxeo

Original poster
Member
Jan 25, 2021
44
Alberta, Canada
So I tried 4 low - it was 100% engaged and there was no vibration. I did notice a 'clunk' shifting back to 4hi - I am assuming that is normal operation due to the torque. No vibration in when back in 4hi.

Prior to that, I was in 4hi, again, very snowy/icy, and it seemed to vibrate slightly at a red light. When I took off when the light changed, there was a 'clunk' like it engaged fully and then the vibration was gone at every other stop afterward.

I'm still thinking it may be something to do with the actual shifting of the transfer case - it reminds me of when the cases with mechanical linkage would be out of adjustment slightly.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON

Maverickxeo

Original poster
Member
Jan 25, 2021
44
Alberta, Canada
So I think I need to apologize - I believe it may be actually normal! I did a little more testing, and here is what I did/what I learned:

I was in 4hi in a parking lot. I turned very sharply and felt it hop (too much traction). I pulled into a spot and it vibrated. Put it in 2wd and it clunked and stopped vibrating.

This leads me to believe that it actually has too much traction in 4wd, which is causing binding, which in turn is causing the vibration? It could also explain the 'clunk' while going through some intersections or when going back to 2wd as the drivetrain unbinds. I've never seen/felt that before, but on my Jeep(s), I tend to stay in 2wd and only use 4wd when it is really ugly out or offroading.

I guess I am a little paranoid - I'm finding problems where there aren't any, haha!
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
No need to apologize. Just learning the Chevy feel :biggrin:
 

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