AWD help

[Ty Stud]

On an 07-14 Denali, the AWD transfer case is a straight planetary differential with a 40% Front, 60% Rear torque split. No clutches, no viscous coupling, no locking. Always 40/60 torque split. So simliar to a rear wheel drive vehicle with an open differential, if one wheel is spinning, the wheel that is not spinning gets the same driving torque (which is virtually nothing). So 1) If the rear tires are spinning, and the front ones won't turn at all: Then you can apply the emergency brake to get more drive shaft torque to the rear, which will get you more torque to the front. 2) If the front wheels are spinning, but the rear ones won't turn: You can apply the main service brake while under throttle. Or to get really serious, I suppose that you could get a line-lock kit so you can hold brake pressure on the front's only. The ABS/Stability control system is rumored to have the capability to brake the wheels that are spinning, to get more torque to the ones that are not. But I am not sure if or how well that system works at doing that. Multiple reports of what you observed seem to indicate that it does not work well if at all at doing that.

Awesome thank you for the help also tried the ebrake then figured I better just get to shoveling.

 

[Ty Stud]

Awesome thank you for the help also tried the ebrake then figured I better just get to shoveling.

*almost

 

[thompsoj22]

On an 07-14 Denali, the AWD transfer case is a straight planetary differential with a 40% Front, 60% Rear torque split. No clutches, no viscous coupling, no locking. Always 40/60 torque split. So simliar to a rear wheel drive vehicle with an open differential, if one wheel is spinning, the wheel that is not spinning gets the same driving torque (which is virtually nothing). So 1) If the rear tires are spinning, and the front ones won't turn at all: Then you can apply the emergency brake to get more drive shaft torque to the rear, which will get you more torque to the front. 2) If the front wheels are spinning, but the rear ones won't turn: You can apply the main service brake while under throttle. Or to get really serious, I suppose that you could get a line-lock kit so you can hold brake pressure on the front's only. The ABS/Stability control system is rumored to have the capability to brake the wheels that are spinning, to get more torque to the ones that are not. But I am not sure if or how well that system works at doing that. Multiple reports of what you observed seem to indicate that it does not work well if at all at doing that.

Yup, This is right, And yes the brakes should have applied to the spinning wheels to force torque to the others. I have witnessed it in the snow, By no means is it smooth but the brakes will cycle on/off on the spinning wheels and it works well at "low throttle" applications. You have to be smooth and light on the throttle and awd will amaze you. But remember they are not 4wd and will not do what a 4wd is capable of doing. Im guessing but at 170k it is time for a transfer case chain replacement at a minimum as preventive maint.

 

[adventurenali92]

I stand 100% corrected. The BW4485 is a straight planetary differential. The NV149 in the older trucks has the viscous coupler.

Yes and no. Lol. The Sierra Denali AWD pickups had the viscous coupling. The SUVs did not have a vicious coupling.

 

[67RS427]

Yes and no. Lol. The Sierra Denali AWD pickups had the viscous coupling. The SUVs did not have a vicious coupling.

No viscous coupling used since 2006 and previous... If the Sierra had a selectable AWD system, it was probably the MP 3023 which is also planetary gear sets and synchronizers for shifting. I believe it does have a "clutch" simply for the shift process but it has nothing to do with the drive system which is a planetary and is definitely not a viscous coupling.

*For the OP, try pulling the ABS fuse next time and see if you get better traction. Unfortunately you can't "fix" the open diff up front but I can tell you my truck drives 100x better in the snow and at the track with the ABS fuse pulled which disables traction control and stabilitrac completely.

 

[adventurenali92]

No viscous coupling used since 2006 and previous... If the Sierra had a selectable AWD system, it was probably the MP 3023 which is also planetary gear sets and synchronizers for shifting. I believe it does have a "clutch" simply for the shift process but it has nothing to do with the drive system which is a planetary and is definitely not a viscous coupling.

*For the OP, try pulling the ABS fuse next time and see if you get better traction. Unfortunately you can't "fix" the open diff up front but I can tell you my truck drives 100x better in the snow and at the track with the ABS fuse pulled which disables traction control and stabilitrac completely.

That’s what I was referring to as specifically in the GMT800 trucks using using the viscous coupler versus the AWD SUVs did not have the viscous coupler.

 

[Ty Stud]

No viscous coupling used since 2006 and previous... If the Sierra had a selectable AWD system, it was probably the MP 3023 which is also planetary gear sets and synchronizers for shifting. I believe it does have a "clutch" simply for the shift process but it has nothing to do with the drive system which is a planetary and is definitely not a viscous coupling.

*For the OP, try pulling the ABS fuse next time and see if you get better traction. Unfortunately you can't "fix" the open diff up front but I can tell you my truck drives 100x better in the snow and at the track with the ABS fuse pulled which disables traction control and stabilitrac completely.

Awesome thank you I’ll try that next time I go out thank you.