SMOOTTH DON

Mats Johansson, Engineering and Quality Manager for Haldex, sent me the following email Aug 30, 2004, in response to my query about how the Haldex works on my 2002 quattro TT:

"In normal driving (steady state) you will have a very low torque to the rear, close to nothing but the coupling is prepared for an immediate response to send it to the rear axle.

"We do not have a max split since we are a fully adjustable system. In a theoretical situation where the front wheels have no grip at all (in the air or wet ice) you will send close to 100% to the rear.

"Best regards, Mats Johansson.

Anyone wishing to verify may, of course, contact this Haldex Manager at mats.johansson@haldex.com

TTschwing

Through the Bevel box gearcase in the transmission, the shaft is always turning in exact proportion to the output ratios. You can't disconnect that and get 100% to the rear.
I don't think this is good information..

TTschwing

I think we need to separate the theoretical from the reality here..

The front and rear wheels are connected by Gearing. When the Haldex is fully engaged, that gearing sends power to all 4 wheels in a 50/50 relationship front and rear. There is no viscious clutch in the system that can disconnect either end when the haldex is active..The Haldex can be partially engaged and send less than 50% to the rear, but the front will always run between 100% and 50%.

TTagz

only picture a TT there

<img src="http://www.fstmotorsports.com/jump.jpg">

PracTTical

<img src="http://www.robinson-race-cars.co.uk/Peter%20Wacker%20wheelie%20webpic%202.jpg">

SMOOTTH DON

Oops, forgot there can be no wet ice in NC!

J. Patterson

Totally different systems. Torsen is a differential. Either set of wheels can turn without the other axle turning at all. There will be torque applied to the slower moving or stationary axle, but it does not HAVE to turn, in order for the other axle to turn. The torque split is determined by the gear ratios inside the Torsen relative to the front output shaft and the rear output shaft. If either axle looses traction it still keeps turning but the other axle (the one with traction) still gets torque fed to it at whatever torque split the gearing inside the Torsen dictates. Haldex is more of a viscous coupling. The front axle of our cars is direct to the transmission. Just like a fwd. If the rear axle loses traction----nothing changes as the front already has 100% of the torque, but if the front loses traction, the sensors engage the clutches in the Haldex sending power to the rear also. The front axle is still direct coupled, but now the rear is getting all the torque that the clutches send that direction too. If they hook up with no slippage it is more like a 100---100 split. Like a 4wd vehicle with no center differential. Of course as soon as the vehicle regains motion relative to the pavement the sensors see that and you're fwd again. The variable is the sensitivity and the point--the speed--- and the strength, that clutch engagement occurs at. It is at least possible (don't know if the programming is there or not) for our Haldex systems to ANTICIPATE slippage based on power application and gear selection, and lock both axles together. Torsen does not do that.
I could certainly be wrong about some of this but at least that's the way it looks to me based on the construction of the units.

TTschwing

They may not have traction, but 50% of the power effort is still being delivered there..
You may have 100% traction at the rear, but power is still being delivered to the front wheels (which means the rear cannot be at 100%)...Besides...&gt;<ul><li><a href="https://forums.audiworld.com/tt/msgs/1537423.phtml">You admit you have NO mechanical knowledge....:-)</a></li></ul>

RoberTT-WWCD

regardless of the controller.

TTschwing

Unless there is some magical power generator in the driveshaft somewhere....:-)