[chassis]

Hello all

Here in eastern Pennsylvania there was a little snowfall yesterday.

Wife and I got in the Touareg to have dinner at a local restaurant. After dinner when leaving the parking lot, the Touareg got stuck where the parking lot exit (apron) meets the street. The juncture is a bit of a gulley or gutter, and this depression was filled heavy snow from plows that had been clearing the streets.

Both right (passenger side, LHD) tires were spinning. I found this surprising, because I thought the 4motion system used all Torsen differentials. The front of the vehicle was raised up, "floating" if you will, on the packed snow. It seemed the front right tire had little to no weight on it.

Not much progress was made rocking back and forth, using the shifter to go from R --> N --> D and back again. I was able to get a little more torque to the ground by tapping the brake pedal while the tires were spinning a little. This produced ESP faults on the electronic display between the speedo and tacho. The brake pedal sprung strongly back as the ESP pump did its thing.

The car was finally freed after shovelling a few 10s of kilograms of snow from under the vehicle, and from the strong muscles of 2 17 year old guys.

Questions - what is the center differential design on the T3? Is this typical behavior for the 4motion system, if one tire is not in contact with the ground? How best to get un-stuck from this type of situation in the future?

Thanks for any replies.

 

[yuyueyuyue]

I've always been amazed by the 4motion, probably because I seta low expectation to start with. However I do hear BMW's XDrive is a better system for situations like this. Tires may be another factor too.

On a side note, My T3 does not let me do left foot braking, the ECU cuts power when there's brake input... not a fan of the drive by wire system....

 

[Ebg18t]

Did you turn off ASR?

What tires are you running?

 

[nickm]

Buy winter tires.

 

[ToolmanJohn]

It sounds exactly like you "high centered" the Touareg on a pile of firm snow. Basically the snow held the Touareg in the air enough so there was no weight for the tires to get any traction to the ground. No traction, no movement, so even 4Motion, even 4XMotion, would be absolutely useless in that situation.

In the past, I have high centered a 4Runner with locking center diff and traction control in deep firm snow in my parents driveway. I reversed into 10 inches of old snowfall in their yard, and parked for a few hours while eating dinner. When I came out, the 4Runner was stuck. I even exited the truck and watched the tires turning while idling in drive. No traction. Game over. I had to shovel a few feet in front of each tire so I could move a little and get some momentum going.

 

[ToolmanJohn]

On a side note, My T3 does not let me do left foot braking, the ECU cuts power when there's brake input... not a fan of the drive by wire system....

Yeah, it's annoying. Noticed this early on my 2013 as well.

Don't exceed 2000 rpm when left foot braking. That seems to be the magic number for when the Touareg cuts engine power when sensing brake input. You can brake stand and rev to 2000 rpm, then release the brake and floor the accelerator as quickly as possible and it won't cut engine power. If you get the timing wrong, it falls flat.

 

[roalco]

The Touareg 4motion system does indeed use a Torsen center differential (just like the Audi Quattro system) for a center diff, and open conventional differentials on each axle using the ABS system to transfer torque and power laterally when slip is encountered. A good demonstration of this is here:

. Used correctly, it is an excellent and extremely competent drive system.
Of course, like any vehicle, motion is dependant on road surface friction, and adequate weight on the tires. If you don't have adequate tires, you're stuck, regardless, and if you have done any vehicle recovery, you will know that a vehicle that is high sided, or floating on its body pan (no effective weight on the drive wheels), can take up to three times it's weight, in winching force, just to move it.

 

[ShadowImg]

This comes up in Subaru-land all the time, in exactly the sort of situation you describe. Some "light" reading: Differential FAQ: Read if you are thinking of upgrading! - NASIOC

The most important part you mention in regards to the torsen differentials is that you had a wheel spinning on each axle. Mechanical/helical/torsen - torque biasing - differentials can only bias torque. In the case you describe, it was doing that, but with an open wheel on each side, there was no torque to be made to the ground.

So unfortunately, works as intended in this case. You'd need a locking or clutch type to avoid that, which we don't have - and if you were high centered as well, even that would be of no matter.

 

[FSJ Guy]

That was GREAT that you knew to gently apply the brake when slipping!!!! Most folks don't know or don't remember to do that! :- )

IMO, "electronic" differentials (ones that use brake pressure to send torque to the non-spinning wheel) are useless in snow/sand/mud. I prefer a selectable locking diff for that.

The center t-case diff just evenly splits power to the axles. If you have open differentials on both ends, a locked t-case doesn't necessarily help.

X2 on having good snow tires, too. But sometimes you just need chains! LOL!

 

[e90diesel]

Agree with roalco on all points. I have tested this by lifting one wheel of the ground with the traction control turned off, than wheel will spin all day long. Leave the traction control on and the vehicle will pull instantly pull free.

My gravel driveway is 750' with an overall grade of 15%. The first 100' are a 20% grade. A pu truck requires 4x4 during the dry summer months due to the loose gravel. The t3 won't spin the tires unless I try.

During the winter months with directional snow tires and traction control left on the T3 is unstoppable until snow gets so deep it starts to build up. When that happens I break out my Kubota 3940 GST with R1 tires and plow the whole driveway.

The T3 system works extremely well, just remember that the system as a whole relies on the brake system to provide resistance. Proper snow tires make a world of difference.

 

[chassis]

Tired are brand new Goodyear Eagle LS2. Not snow tires.

Would be nice to have a center lockable diff. But in the high centered case it might not have helped.

Moved the vehicle a little today, during shoveling. The brake pedal was a little soft and the brakes didn't function fully. No warning light on the dash. Will drive some more, carefully, to see if the ESP pump went to Heaven.

 

[e90diesel]

Find a set of used 17" canyon wheels off of a T1-T2, install a set 235/65/17 snow tires on them. It will make a world of difference. A brake issue would cause a dash light.

BTW how many miles are you at now?

 

[BB62]

That was GREAT that you knew to gently apply the brake when slipping!!!! Most folks don't know or don't remember to do that! :- ) ...

So are you saying that when one wheel on both axles are spinning, applying the brakes will help the situation? (assuming that you have a T3, that is)

If not, what is the proper way to handle the situation?

Thanks!

 

[noobytoogy]

Looks very much like tire trouble to start with, let alone any other problem.

This is a typical example of an "all season tire" being totally inadequate in anything other than a light snow fall.

The "all season" description should be banned from tire adverts and accompanying blurb!

With the probable exception of a new Michelin and a new Nokian [not yet available in 4x4 sizes] there is no such thing as a true "all season" tire as these kind of tires are a compromise between summer and winter capabilities.

Look at the road biased/summer biased tread pattern:

GoodyearÂ*Eagle LS-2

And look at the reviews, especially those related to winter conditions:

GoodyearÂ*Eagle LS-2

I see the OP's tires are new but if they were approaching half-worn, their capability would be significantly reduced as grip in all circumstances starts to fall off exponentially as tires wear, something many owners either don't know or choose to ignore.

I don't blame the OP for having high expectations of his Touareg, it's a 4x4 after all which, regrettably, can lead to over-confidence.

Unfortunately it's an experience of this kind that demonstrates the importance of fully understanding your vehicle's capabilities and how to use them, reading the ground ahead, having the right boots on the car for the kind of weather being encountered . . . and having a couple of shovels and a large bag of grit in the trunk just in case!

Just one more thing, people talk about "snow" tires when they are actually "winter" tires.

They are designed to clear water and slush obviously but their key capability over other tires, including those marked as M+S but without the 3 mountain peaks logo, is to remain supple at temperatures below 7C so their tread pattern will work trapping snow in the tread for grip on snow, or squeezing water off ice to give grip on ice.

 

[Yeti]

I hated the LS2's when had them on my Treg. Was not even two weeks after I received it I got rid of them for something much better imo. One guy at the tire store thought i was nuts, but the guy who waited on my understood while I wanted to change them.

 

[chassis]

Brakes seem find now. has anyone had a mushy brake pedal after prolonged ESP actuation such as when stuck in snow or mud?

I hear everyone on the LS2s. Nearly all of my driving is highway and they work for me.

On a sort of related note, I have had sluggish torque converter performance in cold weather after the vehicle has sat parked for 2 weeks (airport parking deck). Has anyone experienced this? The torque converter seems to slip excessively and the vehicle does not accelerate as normal until it seems like some hydraulic fluid has been circulated a bit. Cold fluid? Insufficient fluid level?

 

[ShadowImg]

So are you saying that when one wheel on both axles are spinning, applying the brakes will help the situation? (assuming that you have a T3, that is)

If not, what is the proper way to handle the situation?

Thanks!

No, so, taking the electronic controls out of the equation - which you shouldn't do:

If you have open differentials F&R, there will be no side to side biasing. If a wheel on either side is fully slipping, you will put down no power on that axle. If you have a wheel on each axle fully slipping, you will put down no power.

However, in the case where you have a free wheel (or even 2) on one axle, say both fronts - you have a torque biasing differential in the center. Torque bias is only functional when you have resistance on both axles. If your front slips even one wheel, it will effectively be 0 torque. 50% of 0 is still 0 to the rear. You can overcome this by applying the brakes to create resistance at the front, which can then apply >0 torque even though the wheels are free, which will then provide 50% of > 0 to the rear.

It's a very select circumstance where this will help, especially with open F&R. It's also very difficult to do, because the brake bias has to allow for braking on one side that won't also defeat any torque generated on the other side. Hence this usually only works when you have a front wheel slipping, and the smaller rear brakes can be easily overcome by the torque.

The 4motion controls will already do this, except that they can brake the individual wheel, so basically, it's better at this.

 

[roalco]

Would be nice to have a center lockable diff.

You do have a center locking differential, it's a Torsen differential, which mechanically locks instantaneously and transfers the majority of power to the other end when it senses loss of traction on one end. Much faster and more dependable (no clutch pack prone to continuous wear, no fancy electronics judging wheel spin, no delicate, exposed stepper motor actuator) than the Haldex differential in the 4XMotion two speed transfer case. This is why they are used on HUMMV's.
You were driving with inappropriate tires, in crushed compacted snow, and got high sided and lost enough traction to stop forward motion. Operator error.
If you are going to drive in marginal situations and conditions, understand your vehicle, it's function, capabilities and limitations, and learn and practice the all important driving skills that you need to have, to get there and back safely. No vehicle, regardless of bells and whistles, can compensate for lack of driver knowledge and skill.

 

[Toiler]

Nobody, Nokian make an AT tyre. The Rotiiva. That is what I use in winter. 235/65R17 It is snow flake rated as are all Nokian tyres . I would use a full blown Nokian snow tyre but this is a bit of a cartel over here and prices are rather extreme. The Rotiiva is at normal pricing at least for Oz.

 

[ShadowImg]

You do have a center locking differential, it's a Torsen differential, which mechanically locks instantaneously and transfers the majority of power to the other end when it senses loss of traction on one end. Much faster and more dependable (no clutch pack prone to continuous wear, no fancy electronics judging wheel spin, no delicate, exposed stepper motor actuator) than the Haldex differential in the 4XMotion two speed transfer case. This is why they are used on HUMMV's.

Definitely not how a torsen differential works. If ours is capable of locking, or transferring torque when one end is unloaded, we don't have a torsen.

However, if one set of wheels loses traction completely, the Torsen differential will be unable to supply any torque to the other set of wheels. The bias ratio determines how much torque can be transferred, and five times zero is zero.

TORSEN is a registered trademark of Zexel Torsen, Inc.

And what will sound familiar:

The HMMWV, or Hummer, uses Torsen® differentials on the front and rear axles. The owner's manual for the Hummer proposes a novel solution to the problem of one wheel coming off the ground: Apply the brakes. By applying the brakes, torque is applied to the wheel that is in the air, and then five times that torque can go to the wheel with good traction.