Sure, but it really depends on a lot of things. What the differential is experiencing in that sort of situation is a shock load. Instead of just being subjected to drive torque from the engine, it is subjected to the (potentially much higher) forces responsible for the rapid deceleration of gears/axles etc. With a clutch type or viscous lsd a large enough load will simply cause the clutches to slip, though that still might be too much for the spider gears to survive depending on ramp angles and preload etc. With a mechanical diff, there is nothing that can harmlessly slip so a large enough shock load will break the diff. How big of a load that takes depends on design and manufacture of the diff itself, and how much load it sees is dependent on the car and the impact. The important factors in our case (IMO) are that the weight, power, and tire coefficient of friction are huge contributors to the magnitude of that shock load. If the diff holds up to a 3800lb, 416 hp ISF it will laugh in the face of an AS1, even when jumping over curbs.

Versus an open diff, definitely yes. Versus a locked, viscous, or clutch-pack, likely not as well.

Mechanical LSD is the safest and quietest type of LSD. It is not bad, but there exists better.

Its my big concern, it will also determine how hard the aftermarket will push for more power. Thank you for the info.

Erm, hate to break it to you, but clutch-pack, viscous, and ATB are all "mechanical" LSD's. ...unless you meant to say it another way.

The term "mechanical" is typically used to refer specifically to the Torsen/Quaife/"helical" style of gear-based LSD.

Could classify the viscous as 'hydraulic', no?

Sounds like a potion for confusion. As if clutch plates and hydraulics aren't mechanical. :iono:

As opposed to Electrical LSD, i.e. ACD and then AYC on the later Evo's, or //M-diff on the //M3, et al.

A Torsen is a great choice for HPDEs and street driving. Clutch packs can be inconstant, noisy, and I've had them go on me before. Eaton TrueTrac was the preferred solution, and I loved the one that I got to try out. C5 and C6 road racers with any sort of serious investment in their cars all switch to Quaifes from the stock (clutch pack) LSD.

If you're driving your car hard enough on the street to feel the shortfalls of your Torsen, you're driving too hard for public roads or you've made such a hash of it that you've placed your self in a situation with one wheel on ice or hanging in the air. You're also going to be making a lot more power than stock. I highly doubt anyone is going to find the stocker lacking at stock or bolt-on power levels, especially for street driving.

You have to remember that a Torsen differential can come with different bias curves; that is, they can be designed to transfer more or less torque to the wheel with more grip. The bias ratio is still limited by the mechanical characteristics of the differential--a torque vectoring differential can transfer torque based on a control algorithm. It's a bit like the difference between a carb and fuel injection.

Another thing to keep in mind is that the BRZ/FRS will have stability control. This interacts with the differential. It just depends how the control algorithm is designed... there are many different control concepts and response times that can affect the performance of the system. It gets even more complicated when you are in real world road conditions with varying levels of friction acting on each wheel due to road imperfections, inclement weather, etc. Stability control can help a conventional differential (non electronic) work better by keeping wheel spin down.

Stability control + torque vectoring differential, like you'd find on an R35 GT-R etc, has the most flexibility and is not constrained by so many mechanical limitations. But it's also more expensive, heavier, more complex, etc.

You're spot on for the average Joe. For the discerning rear-drive track rat [rarely applicable], a clutch-pack diff like OS Giken is usually an improvement over a Torsen in measurable lap times [per a Grassroots Motorsports test from a year or so ago]. A clutch-pack diff that's inconsistent or failing is one worth throwing in the bin, I'm sure we can agree easily on that. Next HPDE I'm at with "the 'vette pack" and I'll ask what kind of diffs they're using just for fun.

A Torsen is great for most situations and most people. Also, like arghx7 said, depending on the stability control programming, the Torsen + VSC might use individual wheel braking to effectively simulate a clutch-pack when traction is variable [i.e. one wheel on ice in winter], when the driver is inducing a drift [fun!], and use the Torsen mechanical torque vectoring when applicable [exiting a corner]. The best of both worlds.

Agreed. You can rebuild a clutch pack diff, which you have the luxury to when you've got a race car. Plus they don't completely free wheel when you're out of the throttle.

The issue with the C6s is that the stock clutch packs do not like much more power than stock. If you're road racing a heads/cam Z06 (or a blown LS3 with meth, because you're crazy), you're looking at 530-550whp. At those power levels, save yourself the headache and go with a Quaife (Katech's offering on all of their builds), a TrueTrac (ECS's offering, after having QC issues with Quaifes), or a ZR1 diff (much beefier clutch packs), which is quite a lot more money.

Yes, clutch pack diffs do get worn down quick with elevated power levels [or shoddy design]. In your examples, it's likely the owners aren't fitting appropriately sized clutch packs per their power level, especially if the stock item is barely good enough for stock power. It's all about having the right size hammer for the job :) Good to hear the ZR1 diff is up to the task.


Long story short, the factory Torsen in the AS1 will be a great solution for virtually everyone. I'll be happy with it as the car will be my daily driver. No maintenance, quiet, easy.