Quote:
Originally Posted by ZDan
The same is true of most limited slips, including clutch-types.
Wheelspeed doesn't dictate the amount of "lock" or torque bias, but it's not totally unimportant.
(FTR "wheelspeed" doesn't dictate how much a clutch-type locks or biases torque, either.)
In both the clutch type and the torsen limited slips, torque is transferred from one output to the other via friction. In the clutch-type the friction is between clutch plates, in the Torsen T2 it's between the helical gears and the casing resulting from axial force in these gears.
If you have different rear tire sizes, rear outputs will be rotating at different speeds and this friction will generate heat and wear parts at a greatly increased rate.
Running a smaller-diameter space-saver spare on the drive end of the car with a either type is not a good idea. Tremendously greater heat and wear due to the different rotational speeds of the outputs. They're only intended/designed to operate like that briefly while cornering, not continuously.
A Salisbury clutch-type with low breakaway torque doesn't behave terribly differently from a Torsen. Can be smoother, even...
There is no waiting with a Salisbury/ramp clutch-type either. In both cases the application of torque increases "lock" or bias, so they are both "progressive" in this sense. And in both cases friction is the mechanism for transferring torque from the wheel that wants to spin to the wheel with grip.
Torsens can and do WEAR. And driving on one for a significant amount of time/distance with different diameter tires will accelerate this wear. But I don't think 50 miles normal driving would do anything catastrophic...
|
I do not think you are correct. I am sure Torsen would disagree with just about everything in your post.
I also point out that the space saver spare, of any size, would be completely worn out and down to the belts long before the slightest wear could have occurred inside the Torsen.
Clutch type LSD use a centrifugally activated clamping system of clutch plates, which is why electronically controlling these is preferred. Edit, the clamping system relies on the wedging action of the spider gears or of the spider drive pin in a shaped slot. The effect is as if centrifugal force pushes the side gears apart. Wave type use interlocking circular ramps to achieve the same effect, again as if there is centrifugal force pushing the side gears against the clutch plates. These wave type are speed sensitive in that there must be a faster moving axle to activate the clutch plates.
These LSD are only wheelspeed sensitive and do not engage unless a difference in wheelspeed is experienced. They react to that. They do not limit slip until a preset wheelspeed difference is achieved. Then they lock pretty firmly and any differentiation results in wear and heat. Edit. Clutch type spin up one wheel as they lock. Torsen never do.
Clutch type LSD "bias torque" by braking the spinning wheel against the wheel with grip. This is why electronic systems for limiting slip operate just like a clutch type LSD until both drive wheels lose grip. Torsen do not do this and cannot do this.
Most of the heat inside a open differential comes from the gear speed, nothing to do with limiting slip. Clutch type LSD heat up because they must allow the clutches to slip to permit differentiation. Torsen do not.
Torsen bias torque immediately and are not delayed by waiting for the lower grip wheel to turn more quickly. They react to the torque that the wheel with less grip can actually handle. Clutch type only react to wheelspin. Like haldex, they limit slip but only when there's slip to limit. Torsen do not limit slip, and cannot. They transfer torque away from the tire that might slip but only do so until it does slip. This is the complete opposite of the clutch types.
And Torsen do not wear when they are biasing torque. On the contrary, they simply differentiate as would an open differential while transferring torque. Friction does not necessarily cause wear. Only sliding friction can cause wear and not much sliding goes on inside a Torsen when it is biasing torque.