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Discussion Starter · #1 ·
So I think many of us would not be here if the GRC was FWD, or perhaps even if it was FWD-based AWD like the Corolla Cross (FWD until slip detected)

So let’s talk about the pretty trick GR-FOUR All Wheel Drive system

This video does a pretty good job of explaining how it works , as does this forum post (these are GR Yaris specific, but should be essentially the same)

i look forward to seeing how it performs in snow/ice compared to benchmark Audi Quattro and Subaru AWD systems. (Optional) TorSen Limited slip rear AND front differentials are pretty trick and certainly help keep the torque at the tires with grip. Interestingly though…my understanding is that since there is technically no center differential it acts more like a “four wheel drive” with a traditional transfer case and torque split is “fixed” (60/40, 50/50, or 30/70 depending on mode) and doesn’t react to changes in grip (torque or wheel speed) like an Audi TorSen center diff or Subaru center Viscous Coupling. I would expect this to result in highly responsive yet predictable drivetrain response in the snow, though perhaps be slightly slower acceleration on slippery surface than if it had a TorSen center diff?
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With the front and rear LSD's, this thing will probably be as predictable as a 4WD system with LSD's I'm hoping. I was talking to @Jeonsa about it yesterday, but if the GRC is delivered pretty early in winter, I'll be taking it right to Lime Rock's winter autocross and I'll see how it does
 

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Torsens are great - no maintenance and fairly effective - they do have a weakness which is they require some torque to work. On sheet ice or with an elevated wheel they can act fully open, I think I saw some track footage showing inside rear lift but it might have been from hitting curbing. I'd prefer clutch type diffs personally but they come with the downside & cost of maintenance.
 

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Discussion Starter · #5 ·
I like the simple, fixed system since it makes it a lot more predictable. Add LSDs and you just have to learn how to drive it in each AWD mode.
I agree it should be very predictable and responsive. My truck (part time 4WD —so 50/50 split, + helical rear LSD) is responsive in the snow but somewhat unpredictable in cornering because it doesn’t have the ability to “differentiate” speed so the rears are traveling a shorter distance but are being forced to spin the same speed and therefore breaks traction easier than you would expect at times. My understanding is the coupling/clutch system in the GR-FOUR should allow some variance in speed(since it is slipping perpetually) to prevent drivetrain bind
 

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My truck is full-time 4WD with a Torsen limited slip center diff and a locking rear diff. While it can get through snow in "AWD" mode(40:60), I much prefer putting it into 4H which locks the center because it's much more predictable. Hoping this car is similar
 

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One of my favorite things about this car is the fact that it has mechanical LSDs, Yes the center coupling has a tiny wizard controlling how much slippage is going on, however the car should feel much more predictable and raw. Torque vectoring is another word for bandaid, and while yes it often works well, It makes the car have more grip and does the hard work for you. Im not bashing on the technology at all. but that is a HUGE appeal to me on this car. It wont be holding your hand all the time. (or at least you will have the option for it not to do so)
 

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One of my favorite things about this car is the fact that it has mechanical LSDs, Yes the center coupling has a tiny wizard controlling how much slippage is going on, however the car should feel much more predictable and raw. Torque vectoring is another word for bandaid, and while yes it often works well, It makes the car have more grip and does the hard work for you. Im not bashing on the technology at all. but that is a HUGE appeal to me on this car. It wont be holding your hand all the time. (or at least you will have the option for it not to do so)
Totally agree. I'm so happy that you can option the Torsen LSDs on the Core model. Toyota is actually listening to their enthusiast customers and it shows
 

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It’ll without a doubt be slippery in the snow but it’ll be much more controlled than open/open, you’ll be able to correct any sideways action pretty easily. Limited slips can force wheel spin but at least all 4 wheels are spinning 🤘🏻.

Im curious about the engagement ratio in the front lsd and how much you’re going to feel it pushing you out of turns and how smoothly it’ll translate through the steering when getting on the skinny pedal.
 

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Personally, I think LSDs on a car such as this should come standard.
They should but the base Core will be a good intro car if you just want to drive it around on the street in anything but snow. The Core with the PP is what you really need to compare it to the Type R, otherwise the Type R will probably win out
 

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Discussion Starter · #17 ·
Torsen diffs are great on the street. Not so great at the track. That's why the GR Yaris GRMN doesn't come with a Torsen diff. It comes with a mechanical LSD.
I assume you mean “plate-type” LSD vs “mechanical”…Torsen is a mechanical LSD, just different (gears rather than plate clutches)
Torsen is smoother and less like an “on-off” switch…where as plate type is more aggressive feeling and can be 1-way, 2-way, or 1.5-way, and they can “lock” the two sides together more so than helical gear
 

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lolol and yet 95% of the Toyota/Lexus lineup is FWD CUVs. Not hating, those cars make the GR cars possible, just pointing out the irony.
I’m sure Toyoda-san would love to make every single car they sell exciting and soul stirring. But in addition to being the CEO who loves fun cars, he is also the president of Toyota who ensures the company stays in business and remains profitable.
 
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