So what is the Big Diff? (pun intended sorry)

[GenkiElite]

Originally Posted by TheSlickOne17

Lol.

I know that was funny right. I didn't know they only made one diff option for the FRS. I've owned two different diffs for my 240 from them. That's just lolz.

[neurokinetik]

I'm still on the fence about the stock diff in this car. I feel like the lockup is a bit too aggressive and pitches the car sideways a bit too easily on corner exit. I'd prefer something a bit more gradual.

The Torsen in my old Miata was perfect, IMO.

The differential is identical in both the FR-S and BRZ, isn't it? Does anybody know for sure?

[arghx7]

Originally Posted by Erik @ GBox

I would have to agree the terminology used in differentials has lead many to believe that to adequately understand their operation requires some sort of mechanical engineering degree which, while helpful to have, certainly is not needed.

One of the main differences between the Salisbury differential and the Torsen, a bit simplified here so bear with me, would be the Torsen does not offer any lock up on the deceleration side of the differential.

This is a very useful feature of the Salisbury as it allow you to use the differential as a both a source of braking, as well as a component in stabilizing the car during breaking, as well.

Another difference would be most visible on the track under really aggressive driving. Should you actually lift one of the rear wheels the Torsen differential will for a moment send 100% of the power it is distributing to the wheel NOT on the ground. A plate type differential will still maintain drive to both (rear in this case) wheels. This can really make a difference in the handling characteristics and track behavior of the car.

This is why you will typically see the Salisbury style differentials in nearly all racing applications when the series rules allow for it.

I appreciate the comments keep them coming.

Erik Johnson

These comments only apply if you have traction and stability control off.

[Crossover Auto]

Also, to note there is a big difference in routing maintenance and break-in on torsen vs clutch plate LSD's. You must change the differential gear oil on a strict basis depending use on clutch plates, generally speaking, more frequently and sooner. In addition, clutch plate LSD's require a break-in method, usually driving in a figure 8.

In summary, for street and daily driven cars, a torsen is best. For track applications, the clutch type will be best.

[TheSlickOne17]

Check out the OS.

It will not let u down.

[Captain Snooze]

Originally Posted by Erik @ GBox

would be the Torsen does not offer any lock up on the deceleration side of the differential.

Please bear with a diff noob here. I thought a Torsen type diff used gears to transmit torque to the wheel with the more traction. Why wouldn't this occur under deceleration as well acceleration? Torsen = torque sensing.

Originally Posted by Erik @ GBox

This is why you will typically see the Salisbury style differentials in nearly all racing applications when the series rules allow for it.

I'm not sure Quaife would agree with you there.

[Mobius357]

Torsens work using helical(worm) gears. What makes the diff work is that worm gears only work, and not work, in one direction each, that is also the downside. Think of the usual use of a work gear, to give huge amounts of gear reduction, in a set that can only be turned from one end. You turn the shaft the worm gear is on, driving a spur gear at a much lower speed. If you try to turn the shaft the spur gear is on, you can't. In a Torsen diff, power from the engine is basically trying drive a set of worm gears by turning their mating gears, but working backwards, under a braking load, those those worm gears a driving instead of being driven, so in that situation it work like an open diff.

As i've been able to wrap my head around, that's the basic gist of it. I'm no engineer, just a generally mechanically minded bloke that likes to take stuff apart to see how it works.

*EDIT* Heres a page that give a better explanation...and a lego torsen model
http://individual.utoronto.ca/stehlik/torsen.html

[Rayme]

Originally Posted by neurokinetik

I'm still on the fence about the stock diff in this car. I feel like the lockup is a bit too aggressive and pitches the car sideways a bit too easily on corner exit. I'd prefer something a bit more gradual.

The Torsen in my old Miata was perfect, IMO.

The differential is identical in both the FR-S and BRZ, isn't it? Does anybody know for sure?

I'm happy that they've actually put in a LSD as a standard equipment.

I do find it a bit aggressive also when doing sharp turns, maybe it's just the low grip tires making it worst?

It will be nice in the winter though, better acceleration on snowy slushy road.

[DarkSunrise]

I remember back when I used to own a GR STI, it had helical front and torsen rear LSDs. This setup worked ok, but you could still get the car stuck in snow/ice if either the left or right half of the car had no traction. As mentioned above, a torsen (or helical) differential will not distribute torque to the slipping wheel if it has 0 traction. With my FR-S, I've spun my inside wheel applying power in hard turns on rainy days. Just a limitation with the torsen-type LSD.

Some of the older GD STIs (I think 04-05) had a clutch-type LSD in the rear. Not only worked well in snow/ice, but apparently made a large difference in reducing understeer as well.