I recently did VLSD swap in my G37x sedan. However this write up can help non-x as well. I have received some question involving it thus it would be easier to make a post for future reference.

The G37 comes in 3 different diff flange type. The X has a 6 bolt flange type. The 7AT rwd has a 3 bolt flange type and the MT has a 4 bolt flange type. IDK anything about the 5AT models.

Due to this we have to make modifications in order to use diff with other flange types.

Here is the secret. All the flanges are interchangeable. There is a center nut on all the flanges. You'll have to measure the amount of torque it takes to loosen this nut and remove it (i think the range was 60ft-lb to 120+ft-lb). Once you have it removed you can use a puller to pull out the flange. The center shaft of the pinion is even center drilled for the use of a puller. Then simply swap the flanges torque the center nut back to your measured spec and install the diff.

The 6 bolt uses a ball and socket to center the drive shaft.
The 4 bolt uses the inter bore of the flange and a lip of the drive shaft.
The 3 bolt uses a extended shaft on the final drive pinion to center the drive shaft.

Due to this you can easily interchange between the 6 and 4 bolt flange types but not 3 bolt.
If you have a 6 or 4 bolt flange diff and want to switch to a diff with 3 bolt flange you'll have to cut off the excess shaft that was used for centering, or else the centering shaft will hit your drive shaft.
Picture below:


In my case I left about 1/8" of shaft above the top thread. Try to make a clean cut and use a center drill on the shaft for future removal

If you have a 3 bolt flange diff you can only use another 3 bolt flange diff without changing the drive shaft.

Something to note:
if you have a AWD don't change the final drive ratio of the of the rear diff. Your front and rear ratios have to be the same.

Review:
After I installed the VLSD on my X I noticed I can recover from much greater slip angle then it could before. This test was done in snow. Since the AWD already have so much grip in dry conditions I don't see this diff making too much of a differences unless you are going FI or want to be a snow drifter.

 

This is interesting

 

I made a mistake.
This should be in "Engine, Drivetrain & Forced-Induction" section.
Could a mod please move it for me?

 

Sure, no problem. Nice thread w/ good info.

 

Here is a question I haven't been able to answer yet, maybe your research has brought the answer to light.

Does the G37XS coupe come from the factory with a LSD?

There is conflicting information released by Infiniti. It seems like they would not do this since the AWD system would likely need to be reprogrammed to have these systems work together effectively without combatting each other.

 

All AWD G uses the 6 bolt diff, and the 6 bolt diff does not have a VLSD option from the factory. The AWD system only controls the torque vectoring for the transfer case since VLSD =/= electric diff.
So the AWD system can only help with wheel speed differences from the rear and front wheels. Not right and left.

With the VLSD your rear diff is also limiting wheel speed differences from right and left now. This is a mechanical system that does not require any electronics.

 

I have been also looking into this lately as well as swapping in some 4.08 gears. Question is, 2008 G35 sedan 5AT, from looking at a couple pictures of diffs it looks like my diff (non lsd) has a 3 bolt flange. Would this mean if i picked up any LSD diff from 08-11 it should be a direct bolt on?

Thanks

 

HA! Applause.. I asked about this about 8 months ago. Someone had the ***** to do it.


More importantly, how does it drive now? How have the dynamics changed? Have you had a chance to corner hard?

Do you feel any differences in drivetrain?

 

I don't know anything about the G35 diff, it might be direct bolt on or might not be. My guess would be its pretty likely since it uses the same chassis. If you have a AWD do not change your final drive ratio. If you really want too, you must match the same ratio to the front diff.

My G37x w/ Michelin PSS tires has a enormous amount of grip in the dry. I don't have the skill nor the ***** to break loose the car in the dry. Thus I can not comment on the dynamics in the dry (FYI VLSD/LSD only changes the dynamic of the car when your wheel slips).
However I did have the chance to test it in the snow last winter. Before the G37x was already a sideways monster in the snow, however the max slip angle was not as large as some other AWD I have driven before. With the VLSD my max slip angle has increased however it also requires more throttle to oversteer now.

 

Per Infiniti's website, they state that the VLSD is an option on the AWD G37 (last item in the "Power" tab): 2014 Infiniti Q60 Coupe Specs | Infiniti USA

Infiniti also claims that the Intelligent AWD system adds an "active brake LSD". So the G37x can adjust torque from front to rear and right to left. This system, along with VDC, has the potential to compete with viscous or mechanical differentials.

Active Brake LSD is discussed in this video:

VLSD is not technically a mechanical differential (such as Torsen), but I understand what you mean about it operating without software. My concern is that the VLSD allowing the wheels to rotate at different speeds would technically be viewed by the car as "slipping" since it is not aware of the differential allowing this "slip".

 

I think it's just active brake limited slip without the differential doing the limitation like a VLSD would. It's an electronic system applying brake pressure to the wheel that it detects slippage so the power can be sent to the wheel(s) with "traction". This translates to poor performance on the track due to "unnecessary" braking.


Sorry I'm not exactly following what you are trying to say. A good VLSD should do a pretty good job regulating slippage. And V/LSD and open diff alike are supposed to allow wheel rotation at different speed (such as low speed turning) so you dont murder your tires. So with VLSD on, the AWD essentially only needs to monitor and control the front wheels.


Shameless plug... but I have an 08 S sedan 3-flange VLSD 3.692 diff available if anyone is interested

 

I agree with HoldmyMouse. Here just to elaborate a little more.

Active Brake LSD = open diff with the ability to brake each wheel. So if one wheels breaks loose it can just brake that wheel. Its a far cry from a actual LSD, but its cheap to implement since ABS system exist in every modern car, all it needs is software. Toyota has been doing it for ages. If you wondering how the "Active Brake LSD" feature will work with the VLSD, the VLSD will take most of the load off of the brakes if not all (depending on calibration) thus with VLSD you saving uneven brake wear.

Yes, Torsen, salisbury, and a few others uses gears for their locking mechanism (LSD). VLSD uses fluids, much like in torque converters. Thus would you consider a torque converter not a mechanical system? IMO fluid coupling is still considered mechanical. Another crude way of explaining is, VLSD limits speed difference between the two tires while most LSD limit the amount of torque split. VLSD is more gradual while LSD is more on and off. Thus LSD is more popular is track, racing cars, and essential for drifting while you find VLSD is sporty road cars.

Open diff allows 100% of slip to any wheel. Using a VLSD you limit that. Thus a VLSD can only help with the Active Braking.


The link you posted about awd with vlsd is for the Q60, if you can find it for the G37 it would be different.
If anyone question rather they have VLSD or not. Turn off car, chock the front tires, jack your rear tires up, put car in neutral, hold one wheel, and spin the other wheel. If the hold wheel wants to spin as well, you have a VLSD/LSD.

 

Not sure if you can just jack the rear to check due to AWD.

 

Car must be off. The transfer case is basically a electronic diff. Thus the rear can move independently from the front when its off. I have tested this.

 

Comments are above in red as they fit.