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Awd On 2008 Silverado Z71

tylusk

By tylusk
in Ask A GM Technician

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tylusk New Member

tylusk

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Will running my truck in AWD on dry pavement for a large number of miles damage my transmission or transfer case? Basically I bought the truck last year and when I picked it up at the dealership it was in AWD. I've driven it for about 15000 miles and never changed the setting on the selector switch except when I've been offroad. Also I just had it in for its scheduled maintenance, but nothing was said concerning the transfer case. With that said, is there still the possibility of prematurely burning out the clutch package or differential if I continue to run it in AWD? Any advice would be greatly appreciated. Thanks

Matt_ Senior Enthusiast

Matt_

Posted
Posted

you mean Auto-4wd, not AWD right? theres a huge difference.

 

while i would not advise leaving a selectable transfer case in 'auto' mode on dry pavement, if you dont have any problems now you're likely ok. put it in 2WD and change out the fluid for good measure

tylusk New Member

tylusk

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  • Author
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I apologize, yes I meant to say Auto 4wd. But being as this is my first 4x4 with an automatic transfer case, would you mind explaining the difference between the AWD and the Auto 4wd? My truck before this was a 2004 Tacoma which unfortunately died on the side of a gravel road with the cab and frame beyond repair so I am not very familiar with GM products. Thanks for the advice Matt and I will go ahead and get the fluid changed.

Matt_ Senior Enthusiast

Matt_

Posted
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No problem. AWD is designed to work on dry pavement, 4WD is not. Basically AWD is like having a differential in the middle of the truck and will allow the front and rear driveshafts to spin at different speeds (which is required when you're turning. 4WD transfer cases lock the front and rear driveshafts together with a clutch system and thus cause parts to bind when going around a turn.

 

At least for the system that was in the GMT800 trucks, when in Auto-4WD mode you're in 4WD when starting from a stop. After a certain speed (maybe 10mph.. cant remember?) the truck goes into 2WD and will engage 4WD if any wheel slippage is sensed.

 

In my 2005 I would instantly know I was in Auto-4WD if I was in a parking lot making a turn. I also used to have customers bring their trucks to the shop and complain that "something doesnt feel right when turning"... the common solution was that they left Auto-4WD on.

 

 

Edit: lol just to clarrify... GMT800 means 1999 through 2007 body styles. GMT900 is the 2007.5 and new trucks.

tylusk New Member

tylusk

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Thanks for the clarification Matt. I'm not sure about the GMT800 series but on my 900 the only thing I noticed while engaged in Auto4wd was that the steering response seemed to be highly sensitive or at least greater than what you would expect from a full sized truck. I never experienced any binding or reduced turn radius like you would normally get while in 4H or 4L. Once again thanks for the info and have a good one.

VMax2007 Senior Enthusiast

VMax2007

Posted
Posted
No problem. AWD is designed to work on dry pavement, 4WD is not. Basically AWD is like having a differential in the middle of the truck and will allow the front and rear driveshafts to spin at different speeds (which is required when you're turning. 4WD transfer cases lock the front and rear driveshafts together with a clutch system and thus cause parts to bind when going around a turn.

 

At least for the system that was in the GMT800 trucks, when in Auto-4WD mode you're in 4WD when starting from a stop. After a certain speed (maybe 10mph.. cant remember?) the truck goes into 2WD and will engage 4WD if any wheel slippage is sensed.

In my 2005 I would instantly know I was in Auto-4WD if I was in a parking lot making a turn. I also used to have customers bring their trucks to the shop and complain that "something doesnt feel right when turning"... the common solution was that they left Auto-4WD on.

 

 

Edit: lol just to clarrify... GMT800 means 1999 through 2007 body styles. GMT900 is the 2007.5 and new trucks.

 

 

You sure about that? I have had Auto 4wd since 1999 and I have never noticed any binding on dry pavement while turning with Autotrac engaged. I am pretty sure it is always in 2wd until slippage is sensed.

Matt_ Senior Enthusiast

Matt_

Posted
Posted

Yea im pretty sure about that. I looked into it and read a tech doc about the system that explained the binding. Also, its not as noticeable on all vehicles: i remember a statement along the lines of "Some vehicles may exhibit binding etc etc. This is normal for the system." however, there were a few iterations of the controls so im not sure if this was a feature for 03+, i dont remember the date range effected

VMax2007 Senior Enthusiast

VMax2007

Posted
Posted
Yea im pretty sure about that. I looked into it and read a tech doc about the system that explained the binding. Also, its not as noticeable on all vehicles: i remember a statement along the lines of "Some vehicles may exhibit binding etc etc. This is normal for the system." however, there were a few iterations of the controls so im not sure if this was a feature for 03+, i dont remember the date range effected

 

Well, find that tech doc then. Cuz until I see it, I am calling :lol:

 

I'll bet an e-beer ( :thumbs: ) that it's always in 2wd until slippage is detected.

Matt_ Senior Enthusiast

Matt_

Posted
Posted

what are you basing your opinion on? that your truck never experienced binding? i forgot, your truck is representative of every truck built by gm....

 

i cant find that tech doc online and i no longer have access to Mitchell. maybe rob or someone that has access and can do some searching for it.

 

i guess your truck never experienced loss of power steering either, which was also deemed 'normal' by gm and i do have the tsb for that...... .but maybe that tsb is wrong because jeffs truck never experienced it.

VMax2007 Senior Enthusiast

VMax2007

Posted
Posted
what are you basing your opinion on? that your truck never experienced binding? i forgot, your truck is representative of every truck built by gm....

 

i cant find that tech doc online and i no longer have access to Mitchell. maybe rob or someone that has access and can do some searching for it.

 

i guess your truck never experienced loss of power steering either, which was also deemed 'normal' by gm and i do have the tsb for that...... .but maybe that tsb is wrong because jeffs truck never experienced it.

 

 

No, I am basing it on how I understand AutoTrac to function. Feel free to prove me wrong, but until then, I am calling BS.

 

But thanks for being a dickhead! :thumbs:

Matt_ Senior Enthusiast

Matt_

Posted
Posted

in lamens terms, the truck is in 2wd until it senses slipping. a few years ago people were complaining about binding when in auto mode. gm released a tech doc that said to imrpove system performance some torque is applied to the front until the vehicle starts moving and that this binding is normal for the system. they even said it will not result in damage but i dont believe that aspect of it.

 

i guess im a dickhead because i dont have a copy of this report and im basing my posts on diagnostic work that i performed as a tech, not just on "well i had a truck once that...."

 

not going to argue with you about, readers can choose what they want to believe... theres another thread where someone said they notice slight binding when in auto mode, i guess their truck is broken or something

VMax2007 Senior Enthusiast

VMax2007

Posted
Posted
in lamens terms, the truck is in 2wd until it senses slipping. a few years ago people were complaining about binding when in auto mode. gm released a tech doc that said to imrpove system performance some torque is applied to the front until the vehicle starts moving and that this binding is normal for the system. they even said it will not result in damage but i dont believe that aspect of it.

 

i guess im a dickhead because i dont have a copy of this report and im basing my posts on diagnostic work that i performed as a tech, not just on "well i had a truck once that...."

 

not going to argue with you about, readers can choose what they want to believe... theres another thread where someone said they notice slight binding when in auto mode, i guess their truck is broken or something

 

 

WTF is a "Lamen"? :lol:

 

I never once said my opinion was based on my truck. I simply stated I have never experienced binding while in auto 4wd. My understanding of Autotrac is based on what I have read about how Autotrac works and I never once claimed it as absolute fact. I simply said until you provide some FACTS, I am sticking with my belief.

 

Now, kindly go **** yourself. :thumbs:

 

Edit: Oh and BTW, earlier you said "when in Auto-4WD mode you're in 4WD when starting from a stop" and above you said "some torque is applied to the front..." Which is it?

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