Since the 3.7 is still on order, I was considering the 3.9 (nismo or central20) to go along w/ the quaife lsd.

My driving is pretty much 50/50 city/highway driving. My average mpg right now is 16-20 and that is a concern. However, I woudl like a taller fg to get to the VQ's sweet spot sooner. Currently, I'm running the stock 3.5 fg w/ the vlsd and would like some higher revving to compliment my lightweight flywheel.

I was pretty much sold on the nissan 3.7 (seeing that the new G sedans are using it and Andy's (perf. nissan) Z is using it as well, but now am also thinkign about the 3.9. Will I even feel the jump up from the 3.5 to the 3.7, or is it a good compromise?

What do you guys think?

 

3.9 seems much too high for my taste.. remember the 5AT comes with a 3.3 and the 6mt with a 3.5.. if i were only concerned about performance tho i'd go with the 3.9

 

With the 3.917 and the 6MT, I think your highway rev's will be around ~3300 rpm at 80 mph. I have it with the 5AT and it puts me at almost 3600 rpm. 3.7 will be a bit lower.

You'll feel more of a difference with the 3.917, but you'll have to ask if yourself if you're comfortable with the higher engine revs depending on the kind of driving you do on a daily basis.

 

poll should indicate AT or MT... MANY MTs have reported great things with the 3.9 FD... however that’s too extreme for AT. The other consideration is that most that have gone 3.9 bought aftermarket which is considerably more $$$ than OEM 3.692 FD.

I don’t know if there is an OEM 3.9 as I was not interested in that short of a gear... but I presume the MT guys that have gone that gear have researched

I'm AT and going 3.692 (3.7)...

 

I don't know if the 3.917 is too extreme for the 5AT. The 5AT is geared in a similar fashion as the 6MT, except its using 3 underdrive gears, instead of 4. If you compare the transmission gear ratios, 1-3 on the 5AT is about as equally spaced as 1-4 on the 6MT. 4th gear on the 5AT and 5th on the 6MT are both 1:1 gears, only 6th gear on the 6MT is a little taller than 5th on the 5AT.

The only time I go, I wish I had gotten the 3.7 gears is when I'm doing 90 mph on the highway and I'm around 3900 rpm. But that's not too often. I hardly go over 80 mph when cruising on the highway anyway.