masco":338i9a4h said:
In our stock transmissions, the front and center differentials are open differentials with spider gears and are built into one unit. You cannot add just a front helical, as spider and helical differential designs are incompatible. The viscous coupler, located beside the front/center diff acts on the open center differential to provide limited slip duties. I'm assuming this new design might use the space reserved for the viscous coupler for the the center or front differentials. In other words, im not sure if this new design will still house the center and front differentials in the same unit.
The rear end is a seperate unit and you're free to do whatever you want to it.
Helical differentials are a 50/50 torque split, until slippage occurs, in which case they are able to multiply the torque applied to the slipping wheels by the torque bias ratio (TBR) of the differential and apply it to the wheels with grip. They are infinately variable and instantaneous. For instance, a helical center differential with a TBR of 4:1 will be able to deliver up to 4 times the torque of the splipping drive side to the side with grip. Since helical differentials are simply torque multipliers, they act as open differentials when there is no traction (resistive force) on one side. It would be great if we could retain the use to the viscous coupler for use in those situations, but if it was active the whole time it would reduce the torque biasing properties of the helical differential itself. There are some companies that make hybrids.
Each type of differential is has it's pros and cons so please do your homework. In anycase I hope i've cleared some stuff up.
I can't see why we could not use it alongside the torque sensing center diff.. (In my understanding the torque sensing diff will sense torque rather than actual speed difference. So the torsen diff could do its job unaffected by the viscous coupler.)
Scenario 1:
If we get wheel spin on the front wheels the torsen will almost have been beaten in the job of securing traction. In a case like that the viscous coupler will help the torsen to limit speed difference on the axles.
Scenario 2:
The grip/torque difference available in front and rear is present but not great enough to make any wheels spin.
Then the torsen will do its job as it uses to, and the viscous coupling will do "nothing" because there is no speed difference between front and rear.
So I my opinion the torsen front center and whatever you would like in the rear + a uprated viscous coupling would be the best "traction retaining system" that you can get for a "street/auto x (all other than dragrace) -car".
It will not lock up the drive-train during parking and such.
It will last forever without servicing parts (maybe except viscous coupling, but think the uprated one will last for a long time). (If you don't brake something)
All this is my way of understanding it, and may be totally wrong.