Is it possible to install the final drive (4.08 or 3.9) gear on a 5 AT with VLSD (sport). Its possible on a MT G37 and the 7 AT.
I been toll that the MT and AT (w/ VLSD) differentials have same part numbers.

 

It is possible. I am looking into that right now trying to get more info on it but it can be done.

 

Can anyone shed some light on this?

 

I can't shed light on what will fit, but as the owner of a 7AT ... why would you want to? The stock 7AT first gear ratio is already pretty agressive (4.92x3.36 final drive) vs. 6MT (3.79x3.446 final drive). First gear in the auto is better than the 6MT retrofit with a 4.08 final drive. This is why the 7AT tends to be slightly faster to 60 vs. the 6MT - you have a lot more torque multiplication in first gear, more than enough to make up for the parasetic loads and losses of the AT. IMHO putting a 4.08 in the 7AT would be pretty extreme.

 

final drive either with 4.08 or 3.9 have been already done on the 370z 7AT and seem to have positive experiences.

But this post is for 5 speed automatic with VLSD. 5 AT differentials are smaller so cannot do the FD modification. This was also confirmed by some of the Nissan/Infiniti vendors I've talked to, one of them said that swapping a MT differential might make this work but that also involves changing the driveshaft flange.

But 5 AT differentials come in two different types, one with VLSD(Sport) and one without(non sport). The housing with the VLSD is bigger and has the same part # as the MT, this might accomodate the FD gears. Just need someone to confirm this.

 

Where would one get this done if one wanted the FD on their 7at/5at?