hechen507

iTrader: (5)

Yes, this is caused by the difference in front and rear rotation speed. Nothing to do with the rear or front diff, its all on the transfer case.

When you say VLSD allows "slip".. all differential allow slip, just some diff like VLSD, LSD (Limited slip differential), and electronic diff limit the amount of slip.
If you imagine a regular G37 RWD with a open diff. If one of the rear wheel is hanging off the ground without touching and the other wheel is touching the ground. All the power will go to the wheel that is off the ground. the VDC system detects slip, brakes the the wheel that is spinning freely, thus causing resistance, thus leading the car to spin the wheel that is on the ground.

Now apply this to AWD: Imagine if somehow one of the front tires and one of the rear tires are off the ground. If you have a regular G37x (w/ open diff) and you apply power how would the car react? Well first the transfer case will transfer the power to the rear, then it detects that the front and rear wheel speeds difference is greater than its calibration table, thus it sent some power to the front as well, since both the front and rear diff are open diff all the power will go to the wheels that are off the ground since the resistance is so low, the VDC detects this is and brakes the freely spinning wheels, thus the torque is transfer to the wheels that is on the ground. (idk what the priority of the system is. But I would guess it would activate the transfer case before it starts braking the loose wheel)

Now imagine the rear has a VLSD in a AWD system: If given the same scenario.
First the transfer case will transfer the power to the rear, the hanging wheel will spin (for very small amount of time), the fluid starts to heats up by the difference of the two sides, the VDC detect slip and start to apply power to the front, in which case before the front fully engages the both the rear tires are spinning due to the VLSD. The VDC will detect the slip is becoming smaller, it may or maybe activate the brakes depending on when it activates. If it activates early the wheels on the ground will start spinning earlier, if it activates later, the VLSD should be moving the wheels before the brakes kick in. Thus depending on the situation the VLSD could cause the brake not to activate when compared to the same situation with a open diff.
As you can see VLSD can only aid the VDC not harm it.

Can you think of a situation when the VLSD is opposing the VDC? I highly doubt it. At the end of the day "Active Brake LSD" and VLSD does the same job. Just one is fully mechanically controlled, while the other is electronically controlled. Although they both have their down sides.
Active Brake LSD wears out your brakes, heats up your brakes, Unpredictable; we do not know the full programming behind it (maybe in certain situations it is disabled or does not engage as much), thus we do not know how responsive the system is, how does it manage the amount of braking force, maybe it was design for only situations when the car is stuck, and its is also disabled with VDC off.
While the only down side to VLSD is the cost and installation if you don't already have it. Also in extreme cases the VLSD could wear out. In which case it acts as a open diff.


Call it what you will, the main concept is what matters. At the end of the day we are arguing over what the word "mechanical" means. Just from a engineering prospect fluid dynamics is a huge part of mechanical engineering.

I stated "Thus LSD is more popular in track, racing cars, and essential for drifting..."


Addressed in earlier parts.


ATTESA is a architecture (much like different models using the same chassis). Just because the the Q60 comes with VLSD in their awd sport doesn't mean the G37 does too. In fact different features can be easily deactivated, or not included (this could explain why the diff are so easily interchangeable). Much like some engines are detuned from their more expensive brothers or how some models have better exhaust. At the end of the day, I have never heard of anyone saying any G37x has VLSD out of the factory. You can check eBay used parts, different infiniti parts dealers, etc. Never seen such a thing. The only definitive way to know is having infiniti credible information that specifically states the G37x has VLSD. Or as posted above a simple test to see if a G37Xs has VLSD.

HoldmyMouse

I'm not getting Ryne's view on "VLSD allows the rear wheels to turn at different speeds" comment. All differentials (except lockers) are supposed to allow wheels to turn at different speed (to certain degree) hence the name. Regardless of any configurations, G37x, G37s or G37xs will all have wheels turning at different speeds.

In a nutshell... basically with the VLSD, the AWD computer is only monitoring "3" wheels instead of all 4 because the rears will either not slip or both slip together. And by slip I mean rapid speed change between the wheels and not just turning at a slightly different ratio.

Baadnewsburr

iTrader: (3)

I know this is an old but I was hoping the OP or someone who has done this could clarify this last statement. OP did you get a different drive shaft?

I thought the whole point of the "secret" modification (i.e. swapping the flange and cutting down the guide) was so that you could mate the VLSD with the 4 or 6 bolt drive shaft.


I think I was following along with everything the OP was saying except this last statement

Did the OP mean to say

" If you have a 3 bolt flange diff you can only use another 3 bolt flange diff without changing the drive shaft unless you do the flange/centering pin swap/mod"?

Baadnewsburr

iTrader: (3)

^ anyone?

Mattlorentzoe

iTrader: (4)

Sorry to dig up old thread but I have a question.

How do I swap successfully 3.9/4.08 final gear ratio into my x?
Nobody makes a front one made for g37x?
I think the rear is same a g37 rwd but what do I need to make front the 3.9/4.08 or something

xscoupe1985

As of now, no, you cannot. Nobody makes gears for the front. It sucks cuz I wanna do 3.69 gears. And as far as someone saying that no X came with lsd factory, the Xs coupe has LSD in the rear, the sedan Xs does not

Mattlorentzoe

iTrader: (4)

xscoupe1985

from what ive been told, we can swap in the front and rear diffs from the g35x, which are 3.69, since they have diff gear ratios due to being a 5at. if this is true, im seriously contemplating doing this at some point... either way, when youre done, let us know what was involved and how it went, and the cost if you are comfortable sharing that info.

zer099

iTrader: (2)

Price depend on the labor in your area and the price you get the diffs for. Front labor should only be two to three hours at worst. I've posted the information on which front diffs one can use multiple times. The list includes most AWD HRs (as in VQ35HR not DE engines) with 3.692 gears. You can also confirm your gears by physically turning the input and counting the output spins (should be 3.962 turns of output for every 1 turn of input) and by looking at the door ID car of the donor diffs: the AXLE code should be RC36. Take my advice: confirm you got the correct part. I recommend replacing the seals on your diffs for cheap insurance while they are both out. There is tons of info about swapping out the rear, and our car (the X) is no different there. Front will need to pull the engine, or easier just drop it a couple inches and wiggle her out. Be prepared for 1st and 2nd to be short as hell.

Reference posts:
3.357 vs 3.692 RPM and MPH compare

Original swap information post

Mattlorentzoe

iTrader: (4)

The Pope

iTrader: (2)

Interesting......

Thanks!

pjmjr508

Hello,

Great info,

Have you driven the G in heavy rain or snow, if so how did it do? Other articles I have read on this stated once in snow or heavy rain it unstable, you do not feel this way with your setup with the VLSD & gear change to 3.69 on yours?

Mattlorentzoe

iTrader: (4)

I feel completely in control at all times of the car. Successfully driving or not in snow/rain is more dependent on the tire(my experience based on 5 years of driving this car in all weather). My car would do terrible in snow, and I would slow down a lot in the rain with current tire setup.!
It’s extremely predictable. Only time the vlsd doesn’t do its job is sometimes on track it becomes “less sticky” and feels more “open diff” around turns.

Never done that to me on the street, just during heavy track abuse. No issues other than that! The vlsd swap in the awd cars really helps them compete the the others in the straights or the curves

Mattlorentzoe

iTrader: (4)

Still no issues!!!!

Whitegslut253

So i have a 2013 g37 journey sedan 7spd auto open diff right? Can i swap in a vlsd? How would i go about this?