I remember when i went to the track this spring to see what my car would do. I drove around the water box and the guy asked me if i wanted to do a burnout. I just laughed and said no thanks.

I just pulled up, lined the car up and floored it when it went green and the car just went with no tire-spin at all. Meanwhile my buddy in his 11-sec Mustang in the lane next to me had to do his whole routine of a 2nd gear burnout, heating the tires and still spun like crap. I actually outlaunched him and held him at bay through 1st gear.......then he got traction and blew my doors off. But the AWD launches nice!!

 

THANK YOU ALL for taking the time to help me understand how the "X" fits into the G35.

Again...thanks!

 

I think I said that in my original response

As an addition, what I said implies you were keeping VDC ON. Even if you turn VDC off, the AWD is still working. Even with the VDC off, the slip light can still illuminate. Its happened many times as I've been playing in the snow with VDC off

 

I wish there was a display of some sort that showed the power distribution like on the Acuras with SH-AWD. It would be nice to see how the car reacts to different conditions

 

So I'm browsing the manual and it says:

Starting and driving 5-23
WARNING: Never drive on dry hard surface roads in the SNOW mode, as this will over load the powertrain and may cause a serious malfunction.

What's that all about?? Sometimes when I drive off on cold morning I leave it in SNOW mode for a little while...makes it effortless to keep the revs low and put around for a little bit until she warms up. The only difference besides the slow throttle is that in SNOW mode its 50/50 until 20mph instead of 25/75 until 12mph. What's the fuss about overloading the powertrain?

 

Because in snow mode the trasfer case is pretty much locked in 50/50. In normal mode, there is some slip as the front wheels are only partially engaged (unless there is detected slip and the system automatically locks the AWD).

Any differences in front and rear rotation typically work out by some tire slip in slick conditions. On dry hard road, there is no slip...so if your tire sizes are off a tiny bit, and you put it in snow mode, you can really put some wear on yout xfer case. At least in normal mode, there is some slippage of the fronts so the minor differences don't matter.

 

So you're saying in SNOW mode 0-20mph is the only time the system actually fully locks up the clutches in the xfer case, and this may cause wear and tear on it? The ATTESA E-TS is advertised as a pretty robust xfer case that will adjust power front/rear as necessary when thrashing the car with lots of throttle around corners and inducing slippage, to keep the car under control. I'll be in shock if the clutch pack and/or center diff. is sensitive to putting around under 20mph on dry pavement.

 

I don't know. I am not the engineer that designed the system so i don't know what it's capable of. I'm just using educated speculation as to why Nissan would say not to use SNOW mode on dry pavement.

My guess is that the xfer case is locked 50/50 regardless of slip or not as this is an advertised feature of SNOW mode up to 20 MPH.

If you'v ever owned an older 4x4 with manual 4WD engagement, they also specify to not use 4wd on dry pavement. If you do, you can def hear the tires squeal in protest as the entire drivetrain is basically locked with no slip. The tires end up doing the slipping. In mud and snow this is fine.

I'd imagine the same would be true when in SNOW mode as the snow would serve to be the buffer for the driveline.

When in normal AWD mode, the xfer case is never really fully engages unless there is wheel slip. So right there gives you a little buffer in the driveline to absorb rotational differences.

Like i said, i do not know, but based on what i rear about the capabilities of the system, that is my best guess which i think it pretty reasonable.

Needless to say, if the manual says not to do it...i wouldn't do it.

 

I'd say its a good guess, too, but I'm curious to hear what others think. Since the xfer case sends power to the front driveshaft via a wet multi plate clutch pack and not by mechanical gears, I speculate that the ECU will not lock the clutch pack to the point of not allowing any slippage. I surmise that there should still be wiggle room, even when engagement is at maximum (for the 50:50 split), to compensate for any rotational differences front to rear. This clutch pack should be the weakest link in the chain, and take up any of these differences without causing wear and tear on the gearsets, just as the typical clutch in a stick shift car will usually slip and fry before your gears are damaged.

"Inside the transfer case a chain drives a multi-plate wet clutch pack, torque is apportioned using a clutch pack center "differential" (the system thus does not involve a regular gear differential as in a full-time 4WD layout, but rather a center clutch), similar to the type employed in the Steyr-Daimler-Puch system in the Porsche 959."

*Edit: Another reason why this is puzzling is that many Skyline GTR's run staggered wheels with the stock drivetrain, don't they? In that scenario, the clutch pack would have to cope with a constant rotational difference front to rear.

 

Skyline GTR's might be staggered wheels, but that's just the tire width. the actual diameter is what matters for AWD. you can have 305's in the back, just that you need the same tire and wheel diameter.

 

Except that the GTR does not have a snow mode, so the xfer case is not locked in a constant state of 50:50 which.

In normal mode, the ratio is changing dynamically, which is why i don't think rotational differences F&R are as vital in this situation. Once in a while, normal mode does lock 50:50, but it doesn't stay constant and eventually reverts back to some form of slipping the clutches to reduce power to the fronts.

I dunno, now i'm confusing myself here, but i think SNOW mode can be damaging to the car if used where the tires cannot slip slightly....ie in snow.

But like i said...i'm not a nissan engineer, so until one of them comes in and tells us, we are regurgitating info we have read on the system secondhand.

 

Interesting....I checked out the Porsche 959's PSK (Porsche-Steuer Kupplung), which is one of the most similar systems to the ATTESA E-TS, using multiple clutches to send power to the front.

"The 2 frictional plates of each independent clutch are rotating relatively to each other. When apply hydraulic pressure to the first clutch, a small amount of torque will transfer to the front axle. But note that the two driveshafts cannot be fully locked up unless all 6 clutches are locked simultaneously. Now, you may see how it works: lock up 2 clutches, 3 clutches ... and the torque to front wheels will be increased, subsequently, torque split could be 50:50 if all the clutches are fully engaged"

When questioned about energy loss and wear due to the slipping clutches: As the speed difference is very small, Porsche claimed energy loss is no greater than 0.4% of the power developed by the engine. As for wear, the clutch is dimensioned that it was negligible and caused no problem during the whole life span.

In the end, its really a question of whether Nissan accounted for some minor clutch slippage when all the clutches of a G35X are locked together for the first few mph of SNOW mode. It only makes sense that they would, yet the manual hints otherwise. I'd love to know the real answer!

 

me too

 

This thread has several members claiming to have run different diameters front-rear on a G35X with no problem.

https://g35driver.com/forums/g35-sed...staggered.html

"u can run a 3% (max, it might be 4% or 5% though...) diameter difference before the VDC will notice anything at all."

"235/45/18
265/40/18
I run/ran on my X no problems."

So if its true that Nissan didn't account for that, then I hope these members knew not to engage SNOW mode

 

I think what happens is alot of people confuse VDC with AWD. They are related, but not the same system. VDC is traction control, ABS and Vehicle stability control while AWD is simply AWD. They work together, but not the same thing.

Most modern ABS systems have a 3-6% threshold of front to rear tire diameter before the ABS will fault and the VDC/ABS will display an error.

AWD, i believe, is tighter than that. I know with GM products, they have a 0.1" MAX difference allowed, and the dealer recommends replacing all 4 tires at once because the difference between the new fresh tires and the old worn tires on the back was enough to mess up the system and cause chatter.

Of course the nissan system works differently, and since in normal mode the clutches always have some amount of slip, it may not affect things as much. Hopefully, if someone with a 3% difference in diameter puts the car in snow mode...they are actually in snow so the tires can slip slightly to make up for the difference in diameter when the xfer case is locked in at 50:50.

My recommendation has always been to use the exact same diameter tires with any sort of AWD/4WD system. There are always going to be manufacturing tolerances and differences on the diameter however...but still, tires are always cheaper than Transfer cases. I have yet to hear of anyone trashing theirs on different size tires, but most of these cars are just coming into the hands of owners who want to modify them with different wheels and such, so the jury is still out.