"Stabilitrak" vs. rear locking diff (2004 Yukon XL)

[up4travel]

Can someone explain "stabilitrak" to me please? My 2002 Yukon XL does not have this, and we're upgrading to the 2004.

Do I really want this, or should I order my 2004 w/ locking differential?

Help!!!

Laura

[Eggert]

Hi up4travel.
Go with the locking diff.
gotto go now, will post more later
Take care, Eggert

[rzkz8k]

Stabilitrak requires Autotrac and here is how GMC describes each:

StabiliTrak®: helps your vehicle respond more accurately and predictably to your steering intentions. If your vehicle encounters an obstacle, sensors feed data to an onboard computer that adjusts steering, engine speed, and brake pressure to any individual wheel to help keep you on track.

Autotrac®:
Four-wheel-drive Yukon and Yukon XL models feature Autotrac™, which automatically engages four-wheel drive when needed. 2WD models feature an available Electronic Traction Control System for enhanced traction.

I have this system on my 04 XL and I would not want to be with out it, the system saved me three times this past winter on black ice roads.

If you can wait for the 05 models, you will be able to get the locking rear with Stabilitrac.

[up4travel]

Thanks.....I appreciate it. Now I don't know what to do...

L

[Eggert]

Hi, thanks rzrkz8k for the info.
I am interested what happened on black ice, and if you have 2wd or 4wd.

Hi up4travel, I will try no to be too boring...

There are 3 things that you can have the car help you with:
Traction - to get you going
Steering - where you are going
Braking - to end the going
TRACTION
3 kinds of Drive:
2 wheel drive - normal for cars, you use that most of the time
4 wheel drive - used in slippery conditions like mud and snow, may be rain. Eventually gets ruined if used on DRY pavement.
All wheel drive - this can be engaged on DRY pavement. This is usually engaged automatically when needed. The transfer case usually has a 'viscous coupling' to allow for slippage between the front axle and the rear axle speeds.

3 kinds of differentials (and 1 traction control) to get power to the wheels.

Open differential:
This is the cheapest and you have one if one wheel slips and the other has all the traction and does nothing.

Limited Slip differential:
An open differential with one extra feature: When one wheel starts spinning a clutch mechanism in the rear axle will engage to connect the spinning wheel to the standing one. The spinning wheel slows down, the standing one gets going. it will disengage when both wheels run at the same speed.

Electronic Traction Control:
This brakes the slipping wheel to give some power to the standing wheel. Kind of faking a limited slip by braking.

Locking differential:
This is is engaged automatically or manually.
Both rear wheel are locked together and run at the same speed.
Just like with 4 wheel drive, you will wreck this on DRY pavement.
An example for this is the Mercedes Unimog from the fifties, where you have locking levers for the transfer case, and the front and rear axles. This means that all 4 (later U2450 model has 6) wheels go at the same speed. You do this at slow speed in deep mud or crawling over rocks.

Please notice that each wheel will go at a different speed when a car makes a turn. That is why we have differentials, to make up for the difference in speed of the 2 wheels attached to an axle.

STEERING
anything with the ending 'trac' will help you steer.
StabliTrak will brake the left front wheel if you make a left turn and the computer wants to help you.

Autotrac just engages 4 wheel drive when needed.
If tyou don't have 4WD, it will use ETC (Electronic Traction Control) and brake the slipping rear wheel. (see above under differentials).

Please notice that Yukons have 4WD. Denalis have AWD, but no low gear on the transfer case.

BRAKING:
This is the ABS, it will selectively release a wheel from braking until it starts spinning again.
Please notice that you can not steer with a locked up wheel that is not spinning.

CONCLUSION:
My choices - MUST HAVE
1) Autoride Suspension. Hands down, no questions asked. Also gets you load leveling.

2) Denali Style Projector Headlights - I got my pair from the Web for $260. You won't believe the difference.

3) Limited Slip Differential. Don't leave home without it.

After that, in order of importance:
1a) 4WD.
I had a Suburban 4WD with no limited slip. What is more annoying than having a rear wheel spin is to have 4WD and a front wheel and a rear wheel spin.
You still go nowhere, except sliding back down a hill with ice on one side of the road.
2WD with limited slip beats 4WD with open differentials.

or 1b) AWD,
if you stay on the pavement and do not need the low gears in the transfer case. This means Denali.

2) 6.0 liter engine. This means 3/4 ton Yukon 2500 or Denali 1/2 ton 1500.

3) 4.10 rear axle gear ratio. This gives more power by revving the engine higher, it also may cost you 2mpg or so.

My Yukon XL K2500 - 6 liter engine, 4WD, 4.10 rear axle gets 10 mpg city and 14 mpg highway. It also has a lot of zip. My 5.7 liter Suburban was outright lame in comparison.

My only experience with traction control, etc. is a Mercedes Benz 300 4matic. It has a computer network and is unbelievable. It even pushes the gas pedal back up, if you screw up too much...
You may go slow, but where you want to go...

Hope this helps, please post any questions or corrections.
Take care, Eggert

[up4travel]

WOW, Eggert...I printed out your reply, and seriously thank you very much!

Laura

[rzkz8k]

Eggert,
To answer your question, I have a 04 Yukon XL 4WD with Stabilitrac and Autotrac. I got the vehicle in November of 2003 (This is my 4th YukonXL/Surburban). One Sunday evening, late, I went to a snow covered mall parking lot to see if I could loose control of the truck, I couldn't, no matter how hard I tried to induce a fishtail the truck went where I steered it. I was amazed, GM did this right.

On morning driving to work in January I came across a black ice condition. I was driving west on Michigan 59 in western Oakland county. I was in the front third of a traffic pack from the last traffic light, we were traveling around 50 MPH. We came around a slight bend and I saw flashing lights ahead. As the pack approached, I could see several vehicles that had spun out. Before I knew it, all of us were on black ice. The flashing of headlights in my rearview mirror caught my attention and I saw a few vehicles in our traffic pack spinning out of control. Now, a vehicle in front of me was spinning out of control and I took steering action to avoid a collision. Stabilitrac kick in, the throttle became unresponsive and I could hear the sound of hydraulic fluids running on the other side of the firewall. The truck went where I steered and I avoided a collision and a spin out. That scared the heck out of me as you could imagine. Stabilitrac saved me from an accident and possible injury to me and others.

The 04 Yukon’s use power steering fluid pressure for the power brakes and ABS system. When ABS or Stabilitrac kicks in, you don’t hear the typical pumping sound of ABS nor do you feel anything in the brake pedal. In fact, Stabilitrac is so fast and so quite, some folks may never know when it is at work.

After the few saves I’ve had this past winter, I would not want a vehicle with out Stabilitrac.

The girl that sits next to me, her husband was one of the engineers that designed Stabilitac. She told me that in the end, they were only able to roll over a Yukon one time, and of course, that was under extreme testing conditions on the test tracks.

[the blur]

that is all nice an dandy.... but I got my 03 denali stuck in 8" of snow.
I had to call a tow truck and get towed out !!!

it is definately NOT a 4 wheel drive vehicle. I think the coupling in the transfer case is NOT designed for true 4 wheeling... or more than a few inches of snow.

I would hate to try it in mud...

[Eggert]

Hi, I am sorry to hear that.
Your ground clearance is 8.4 inches.
What happened?
Did you ride up on the snow?
Did the StabiliTrac kick in?
I am not sure if the Denali comes with a locking differential. Do you have it?
Which wheel(s) were slipping?
Please let us know.
Thanks, Eggert

[tonytone]

Eggert--nice writeup! You may want to add that the '03 Yukons also offered a full-time 4WD option--essentially, an AWD setup w/ low gear. I know this to be fact 'cuz I own an '03 YXL with said option--no Autotrac controls, but does have Stabilitrac (yes I know it doesn't have anything to do with whether a vehicle is 2WD/4WD/AWD) and a 4LO button (but no 4HI or Auto4WD buttons).

IIRC, and someone please correct me if I'm wrong here--I think the first few model years of the NBS Denalis may have come with a locking diff (RPO code G80, if I'm not mistaken), but '03 (I think) and '04 (I know) don't come with one.

[the blur]

Originally Posted by Eggert

Hi, I am sorry to hear that.
Your ground clearance is 8.4 inches.
What happened?
Did you ride up on the snow?
Did the StabiliTrac kick in?
I am not sure if the Denali comes with a locking differential. Do you have it?
Which wheel(s) were slipping?
Please let us know.
Thanks, Eggert

I thought I was on lightly covered road, but was on 8" of hardpack snow.
eventually the truck dug down into all 8" and I was stuck. 2 wheels spun, and then another 2, they alternated. never did all 4 wheels spin at the same time.

stabil track is NOT for getting un-stuck. the traction control was kicking in. so I disengaged stabil-track which turns off PART of the traction control. I tried everything, but eventually called the tow truck.

[Eggert]

Thanks, blur, for the update.
It looks like a physical limit was exceeded, in this case the ground clearance.
No assist gizmo can go beyond the physical limits.
To expand this limit of ground clearance you would need larger tires and / or a body lift, decreasing handling and safety.
Take care, Eggert

[c52k]

Hi folks,

this is a good thread and very informative.

I currently own a '99 Tahoe LT 4WD with a 4" lift and 33's.

I love the new Yukon Denali's and will more than likely be getting one in the next few weeks.

I've heard that because of Stabilitrak, it is not as cut and dry to add a lift and bigger tires. Is that really true or have i been misinformed ?

I'd like to do the same to the Denali as i have on my Tahoe. 4" lift w/ 33's. I don't do any major off roading but like the extra clearance when i do go to the snow.

As far as the AWD. I can't say i completely understand this. I know if i put my Tahoe in 4 Low or High, all 4 wheels get power and spin. Is that the case with AWD ? Is there an option on the '04 Yukon Denali's to accomplish this if AWD doesn't do this ?

[tonytone]

c52k--the '04 Yukon/Yukon XL Denali AWD doesn't have 4LO; if this is important to you, then these two vehicles (and Escalade AWD) won't do; I don't know if the '04 Yukons offer this, but in '03 GM offered a AWD(technically, it's really full-time 4WD) Yukon that does have 4LO. Other than that, the AWD distributes power 60/40 rear/front IIRC (someone please correct me if I'm wrong here). One other thing--late model Yukon Denalis ('03+, maybe even since '02?) don't come with limited slip/locking differentials.

[c52k]

Thanks for the info tonytone.

4LO isn't a particular feature i'm looking for. It's just i don't have any experience with AWD. My '99 Tahoe had an auto 4WD setting which I never used. When i went to the snow and and conditions required, I would put it in 4HI or 4LO.

If the AWD takes care of that on the fly then that will work just fine for me. From what i understand that's pretty much AWD does. When it senses slip in the rear, it tries to compensate and put some power to the front.