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2019 GMC Yukon XL SLT

Oren0418
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Oren0418 New Member

Oren0418

Posted
Posted

Hi all,

We recently purchased a 2019 GMC Yukon XL 4wd.  We have not driven it much, but noticed that when we switch from 2wd to the auto 4wd system, the car begins to shudder.  It feels like we are driving on a bumpy road or over small gravel.  It does this at low speeds, while accelerating and at highway speeds.  It drives smoothly in 2wd and we are wondering if this is normal or an issue with the 4wd system?  It shudders similarly while in 4wd high, we only tested this briefly as our roads are currently mostly dry and we have no snow/ice (and have not tried 4wd low). Thanks in advance for any help/comments.  

CamGTP Senior Enthusiast

CamGTP

Posted
Posted

The auto 4 wheel drive will still be in 2wd until the rear end slips, like on ice/snow then it engages the front axle. It should not shudder or vibrate going straight down the road or turning in 4AUTO.

 

That new of a vehicle will still have a warranty, you should take it into the dealership.

  • Thanks 1
JimCost2014 Senior Enthusiast

JimCost2014

Posted
Posted (edited)
6 hours ago, Oren0418 said:

Hi all,

We recently purchased a 2019 GMC Yukon XL 4wd.  We have not driven it much, but noticed that when we switch from 2wd to the auto 4wd system, the car begins to shudder.  It feels like we are driving on a bumpy road or over small gravel.  It does this at low speeds, while accelerating and at highway speeds.  It drives smoothly in 2wd and we are wondering if this is normal or an issue with the 4wd system?  It shudders similarly while in 4wd high, we only tested this briefly as our roads are currently mostly dry and we have no snow/ice (and have not tried 4wd low). Thanks in advance for any help/comments.  

Welcome to the site.

 

Take it in while it is still under warranty, could be numerous things going on.

Edited by JimCost2014
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BlaineBug Enthusiast

BlaineBug

Posted
Posted (edited)

The front axles still become engaged in auto, and I don't believe that it is true that it will operate in 2wd until there is slippage.  In auto there is a clutch inside of the transmission that disperses power between front in rear similar to an all wheel drive system.  Only when you switch to 4 HI or 4 LO does it fully lock the front and rear together.

Edited by BlaineBug
k-man21 Enthusiast

k-man21

Posted
Posted

Unless you know you're going to be in a situation you may need 4x4, there is no reason to ever have the car not in 2wd. Leaving it in "AUTO" spins a clutch and I believe the front differential as well, hurting the gas mileage. If you are worried about slippage, then put it into AUTO, otherwise, leave it in 2WD.

  • 3 weeks later...
gat0r Enthusiast

gat0r

Posted
Posted

my '15 has no vibrations when using Auto or 4hi

 

i also have not experienced any difference in fuel economy when driving in either 2wd or Auto

also no noise in Auto on highway

  • 2 weeks later...
Mikey999 Enthusiast

Mikey999

Posted
Posted

Take to  the dealer  sounds like your awd is engaging  4wd when it shouldn't.    4wd should never drive on dry payment and when  you 4wd on dry pavement  you will  feel unsual vibrations 4wd is just for  bumpy dirt  roads off road or deep snow. Awd should remain  in 2wd on dry unless slippage  is sensed it engages the front.   

BlaineBug Enthusiast

BlaineBug

Posted
Posted (edited)
22 minutes ago, Mikey999 said:

Take to  the dealer  sounds like your awd is engaging  4wd when it shouldn't.    4wd should never drive on dry payment and when  you 4wd on dry pavement  you will  feel unsual vibrations 4wd is just for  bumpy dirt  roads off road or deep snow. Awd should remain  in 2wd on dry unless slippage  is sensed it engages the front.   

That isn't true, correct me if I am wrong.  But when placed in "automatic" mode it simply engages some sort of clutch mechanism internal to the transfer case that, instead of locking the front and rear outputs of the transfer case as one and equally distributing 50/50 power to the front and rear axles, it allows slip between the front and rear.  So on 4x4 it will still be providing power to both the front and rear axles but at varying degrees of split.  And also when engaging "automatic" mode it engages the front axle so that the front driveshaft is spinning and the front hubs become locked.

 

I'm not sure what kind of "disconnect system" exists for the front hubs, but normally when in 2 wheel drive mode, the front driveshaft is not spinning.  I believe there must be some sort of disconnect mechanism within the front differential itself rather than at the hubs like on older vehicles that had common failures with vacuum disconnects or electronic motors mounted to the hubs themselves.

 

All in all, more is spinning and connected when in "automatic" mode so therefore you will feel something different.  I do.

But if you make a tight turn while in "automatic" mode you won't experience the binding that one would if they were fully locked in 4x4 mode.

Edited by BlaineBug
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