Confirmed Torsen Differential

[Jeff Lange]

Sorry, you didn't quote anything specifically, so I wasn't sure how it tied into a differential thread.

Still, the IS300 used a W55, which is actually a relatively beefy transmission compared to some, and while some may have had issues around 300rwhp, most push it further, and that is behind an engine that will put out a lot more torque at 300rwhp than a 4-cylinder would.

It's a relatively moot point though, since the FR-S/BRZ/86 appears to be using the AZ6 (Toyota code J160 in the Altezza when used behind the 2.0L 3S-GE and 1G-GE), which is a lighter-duty transmission than than the W55 even, likely due to wanting a lighter weight transmission.

So while the IS300 transmission could take however much power, it actually doesn't matter in relation to this car, which uses a lighter-duty, lighter transmission.

Jeff

[toyo_]

Good news!, i like Torsen.

[4agze]

I like this news beefy rearend & lsd but for me as soon as I'm done paying & warranties are done its going to be KAAAAAZZZZ

[Dimman]

Originally Posted by Jeff Lange

Sorry, you didn't quote anything specifically, so I wasn't sure how it tied into a differential thread.

Still, the IS300 used a W55, which is actually a relatively beefy transmission compared to some, and while some may have had issues around 300rwhp, most push it further, and that is behind an engine that will put out a lot more torque at 300rwhp than a 4-cylinder would.

It's a relatively moot point though, since the FR-S/BRZ/86 appears to be using the AZ6 (Toyota code J160 in the Altezza when used behind the 2.0L 3S-GE and 1G-GE), which is a lighter-duty transmission than than the W55 even, likely due to wanting a lighter weight transmission.

So while the IS300 transmission could take however much power, it actually doesn't matter in relation to this car, which uses a lighter-duty, lighter transmission.

Jeff

I thought the IS300 had an aluminum-cased W58? Or is that what the W55 is?

[bambbrose]

Originally Posted by Dimman

I thought the IS300 had an aluminum-cased W58? Or is that what the W55 is?

W55 is a W58 with minor differences.

[Ikaros]

Wait, I am really unfamiliar with these tech stuff, but does Torsen mean you can drift easier, and drive safer on terrains like mud or snow?

[JDLM]

Originally Posted by Ikaros

Wait, I am really unfamiliar with these tech stuff, but does Torsen mean you can drift easier, and drive safer on terrains like mud or snow?

http://en.wikipedia.org/wiki/Torsen

[Jeff Lange]

Originally Posted by Dimman

I thought the IS300 had an aluminum-cased W58? Or is that what the W55 is?

The W58 is also aluminum case, the W55/W58 are the same design, just different gear ratios. Depending on the year, there are various synchro/gear/shifter differences, however the difference between a W55 and W58 is the gear ratios.

Jeff

[Dimman]

Originally Posted by Jeff Lange

The W58 is also aluminum case, the W55/W58 are the same design, just different gear ratios. Depending on the year, there are various synchro/gear/shifter differences, however the difference between a W55 and W58 is the gear ratios.

Jeff

Awesome, thanks.


Back to the Torsen, is it true that they can be fragile on road courses or rough streets? I've heard that they will break in an example of hitting a curb (racing curb) or bump and one tire loses total traction, but then hitting the ground suddenly has full traction again.

[Jeff Lange]

That can cause issues with any differential, though Torsens are slightly more prone to break under those conditions, especially T1's, since they are quite a bit weaker. The T2 holds up a lot better, and is what Toyota currently uses. I haven't seen many (if any) T2's broken in a Toyota without ridiculous amounts of torque/drag racing, etc.

Jeff

[old greg]

Originally Posted by Dimman

Awesome, thanks.


Back to the Torsen, is it true that they can be fragile on road courses or rough streets? I've heard that they will break in an example of hitting a curb (racing curb) or bump and one tire loses total traction, but then hitting the ground suddenly has full traction again.

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.

[Ryephile]

Originally Posted by Ikaros

Wait, I am really unfamiliar with these tech stuff, but does Torsen mean you can drift easier, and drive safer on terrains like mud or snow?

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

[ryude]

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

Torsen, which stands for torsion-sensing, LSD's use gears and typically provide more like 75% coupling. The MRT Torsen style front LSD locks under load so provides more grip when exiting a corner, but acts like an open diff under trailing throttle so it does not induce understeer coming into the corner. This is the major difference with a mechanical LSD. Most rally and full race cars use clutch pack diffs as a Torsen LSD is unable to transfer torque if there is none, ie if the wheel is off the ground it will not work, a clutch diff will. A Modena Torsen LSD is a non-adjustable unit that in theory transfers torque from a spinning wheel to the other wheel before it spins.

Point to consider - a torsen LSD, has silent operation and is ideal for street use.

[fa5tco]

Originally Posted by Jeff Lange

Sorry, you didn't quote anything specifically, so I wasn't sure how it tied into a differential thread.

Still, the IS300 used a W55, which is actually a relatively beefy transmission compared to some, and while some may have had issues around 300rwhp, most push it further, and that is behind an engine that will put out a lot more torque at 300rwhp than a 4-cylinder would.

It's a relatively moot point though, since the FR-S/BRZ/86 appears to be using the AZ6 (Toyota code J160 in the Altezza when used behind the 2.0L 3S-GE and 1G-GE), which is a lighter-duty transmission than than the W55 even, likely due to wanting a lighter weight transmission.

So while the IS300 transmission could take however much power, it actually doesn't matter in relation to this car, which uses a lighter-duty, lighter transmission.

Jeff

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