I tried looking through the sticky on gears as well as searching "3.7" and couldn't really find anything... Has anyone tried the 3.7s? Are they really worth it? Reason why I'm asking is because I drive on the highway 3 to 4 days a week (yeah I have an 08 with the 7500 redline but I still like low RPM in 6th). The 3.7s seem like a perfect fit to me but I wasn't sure if they're really worth it or if you even notice the difference... Any info would be great, thanks.

 

none of the gears are going to give you a huge differential when in 6th gear cruising

3.7 is a nice upgrade for an automatic guy, but for a manual transmission, alot of money spent without any real net advantage - its only slightly shorter than the stock 3.54

for the 07 +, the 4.08 is absolutely the way to go IMHO

 

What about gas milage? I usually drive 80 or 85 MPH on the highway...

 

if gas mileage is of primary importance to you, you probably should slow it down by 20mph

there is a whole sticky thread on the various gears right in this section. There is no significant change in mileage at all

 

+1

 

Drive 60 instead of 70 MPH. That should take care of it.

 

if stock is 2k rpm @ 60 mph, what would a 3.9 and 4.08 run at? im in the exact same place as OP, i do a lot of highway driving and i drive 55 to 27-29 mpg, so that when when im spirited in the city the gas mileage will equal out, so im worried that this final gear will raise 60 mph to 2400 or 2500 rpm.... anyone that has these please chime in!

 

https://my350z.com/forum/engine-driv...installed.html

 

Just out of curiosity are there any traction issues with the 3.9 gears? What about gears and a light weight flywheel? I thought I read in the sticky that the 4.08 gears cause 1st to be pointless... But I could have read that wrong. Or I could just be a dumb-***...

 

I guess I should probably rephrase my mileage question... To be honest I don't see myself slowing down anytime soon (I know that is bad). What I'm more concerned about is the effect of driving at say 3,000 RPM for an hour compared to say driving at 3,500 RPM because of gearing. Is it really that much louder? What about added wear and tear on the drive line components? I would imagine you would want to change all of the fluids sooner... Or am I just being overly cautions on all of this?

 

there is no difference in wear or maintenance at all

as far as volume, that really depends on your exhaust I suppose.

 

grip is a function of many things, not one singular item. Tires, alignment, differential, all play as equal a role in traction as well as the gears. I know I have zero traction issues in first gear. I currently have 3.9's, fairly grippy tires (285/30/RE050A), and a Cusco diff with -1.5 rear camber and significantly more hp than stock/lightly modded. I'll soon be trying 4.3 gears with another Cusco diff. (whenever I get the time to put the rear together) as my car is just begging for it - I don't expect any significant traction issues with those either