PA-21 Skater

I finally got a chance to try the SS out in some snow today. My detached garage driveway is slightly uphill grade to the door way. There’s a cement pad in front of the door. Here's what happened today as I was playing in the snow.. got stuck? Both front tires were on the cement pad which didn't have any snow or ice and the both rear wheels were in about 4 inches of snow. Both rears were spinning but the fronts weren't. And yes I could hear the traction control working... bong, bong, bong. Anyone else see this issue yet?



regards,

Blown02Sierra

Next time put the parking brake on or hold the brakes lightly.

Bowtie70SS

iTrader: (10)

The stock tires really leave a lot to be desired. My SS (Silverado) does ok, but I still have the stock Eagles. If you go to tire rack and browse the revidews the Eagle LS tires are horrible in the snow. The next set I get are gonna be some grabbers or something better all around.

Dave

PA-21 Skater

I agree, the OEM tires aren't the best for traction. But shouldn't I have at least 3 tires spinning?


work as a technician for a VW/Audi dealer for over 30 years, and VW & Audi have used the Torsen center diff for many years. It has the ability the by manufacture design to vary the torque split from front to rear axles. By design the spilt can be i.e. 20/80%, 50/50%, 30%/70% or what ever the manufacture wants. So I think GM would have designed the system when the rear wheels were spinning the Torsen would transfer some(%) torque to the front axle, which has the most traction to get you moving. Below is a brief excerpt on how the Torsen works.



Next came the torsen (stands for TORque SENsing) differential, which was embraced by Audi in its second generation quattro system. The torsen diff was invented by an American company (Gleason corp.) It is a fully mechanical device of worm gears and a worm wheel whose workings are quite difficult to describe with words and probably beyond the scope of this article. However, the torsen's characteristics are the issue that is of interest here. The torsen differential will split torque 50:50 in a no-slip condition. However, when one axle slips, the torsen diff will send more torque to the axle with more grip, in other words, it works in an exactly opposite way to a conventional diff. Torque splits of up to 80:20 are available, depending on the pitch of the worm gears. And since it is a completely mechanical device, the locking action is instantaneous and progressive. The torque sensing characteristics of the torsen also allows it to be proactive in preventing wheel spin rather than reactive, in correcting a wheel spin situation. The torsen diff is thus "more sensitive" to slip. Its locking action is also more progressive.

More importantly, the torsen does not lock or inhibit speed differences under braking, thus allowing all 4 wheels to rotate independently at their own speeds when no power is applied. The torsen diff only locks in a power application situation. The torsen has a torque sensing characteristic.

DrkPhx

iTrader: (15)

Thanks for the info. I live in MN where this is still snow and ice on backroads. I drive up a steep hill covered in ice everyday and the AWD will immediately sense the rear tires spinning and transfer power to the front.

zippy

According to the GM manual, the center diff in a TBSS is an open diff, not a torsen.

PA-21 Skater

Here's what I found out from the tech who was nice enough to print info from the GM repair manual concerning the center diff. Under normal driving its a 45%-55% torque-biasing split, but the overall range is 25%front and 75% rear. I'm going to scan the info and post the info here in a few days explaining the operation.

zippy

Here's the basis of the info on it. As we all know, the most important part of it's information is in the first sentence. There is no torque splitting with an open differential. All of the torque splitting is controled by the stabilitrac system. When one set of wheels spin, the brakes are applied to that axle and the torque is supposed to be applied to the other axle set just as experienced by PA-21 Skater. Unfortunatly, it doesn't work like they want it to in most cases.



• The front/rear drive differential carrier assembly is an open differential in the transfer case that is always sending torque to both the front and rear axles. The front/rear drive differential carrier assembly is a torque-biasing devise that senses torque and multiplies it to the other wheel, so if one axle is on a low friction surface and loses traction, the front/rear drive differential carrier assembly applies more torque to the other axle, such as if the rear wheels are on ice, more torque is applied to the front axle, and vise versa.

• This is a true full-time system since it is always active with torque split between front and rear axles so torque adjustments occur instantly and smoothly.

• The ratio of front/rear drive differential carrier assembly application is split with 33 percent to the front axle and 67 percent to the rear axle under normal conditions, but since the system is torque biased, that ratio can range from a more balanced 45:55 split up to a 25:75 split depending on road conditions and driver demands