First off, gears in a FI car can help tremendously. I'm not sure why people are saying that they cant. I cut off damn near 3 tenths JUST changing to a lower gear on my240sx with GT30R turbo. That's with ALL things being equal other than just swaping out rear ends.

Also, the difference in rpm's in your cruising gear in going from a 3.69 gear to a 4.08 should be right at 300 rpms. That is not a huge difference considering you will gain approximately 10% in accerleration. Everybody should plug their tire height, and gear ratio into this calculator on this link to get your exact difference in rpms if you switch to the 4.08 from the 3.69.

Randy's Ring & Pinion. RPM Calculator.

 

oro, I like the way you post. Post more!

Yes, gears can help a F/I car too. But there are a lot of variables involved and then the whole "what are you doing with the car" issue. If the car (with F/I) is making enough power to spin the tires in the first two or three gears, then gears won't help anything. Yes, there is always stickier tires but there is a limit and then we're back to the "what are you using the car for" question.

 

I wasn't being specific... I personally wouldn't want to daily drive 4.08 gears.

 

Exactly. As well a 240 stock for stocks powerband isn't quite as "thick" I'll say as a Z,G35 or G37 for example and the turbos kick in a bit later in the powerband. For example even a 3.5 liter 350Z takes around 3000rpm to hit full spool on a GT35R and that's with an extra 1.5 liters on an SR20. Though the engine does have to pump more air usually larger displacement motors do this faster, so in essence the gears would be a bit more useful to a 240.

As well gears will help tremendously if you can make the car stick, but as IVW pointed out. Gears will take off tenths with FI, very true but if your car is not made specifically for a reason. IE: Drag racing, then that car can be extremely squirrely on an actual road course where your car will have to be specifically tuned by suspension as well to even make use of that kind of powerband, even in drag a 3.5 liter DE motor would have a ton of trouble putting down 600hp with some slicks.

I would definitely check out Alberto's videos on youtube, he is considered probably one of the best if not the best Turbo drag racing Z drivers on My350z. He has videos where even on slicks he is trying to fight his car to stay straight in the quarter, and even backing out of the gas multiple times he still runs 11's, and he actually cut his gears back to the 3.3 rear end gears from the automatics to make better use of keeping the turbo in a higher rpm range.

 

 

Well, yes and no. If your car is spinning all the way through third, then yes, you have the wrong tires on the car. Plus, as anybody who has drag raced a car that has anything remotely considered good power, slicks are a must for the best times. FI or not. Gears or not. But, then we are going back to "what somebody wants to do with the car".

Ehhhh, if he is fighting the car from going sideways with only 600hp out of a 3.5 DE motor, he either needs bigger slicks or needs to setup his suspension correctly. I run a tiny, tiny slick. A MT 26x8.5x15 and I have to launch at 7500rpms just not to bog!! Car does not make quite 600hp, but it does make about 420whp. (11.5@119 with a 1.60 sixty foot before I changed my rear end gear, video on youtube if you want to see it :-) Top that with a Z33 Chassis having MUCH more room for a proper slick and I promise you his "going sideways" CAN be fixed. There are cars with twice his power, driven on the street that have no problem hooking at the track with the proper slick and suspension setup. That way, he will not have to feather the gas to keep the car in a straight line and can run faster times than 11's, cause IMO, a 350Z with 600whp should run mid tens or better easily if the guy can shift and cut a good 60'. I have seen his videos on youtube, and that car seems much faster than an eleven second car.

I guess what I'm also trying to say, is that if you want maximum acceleration, changing the rear end gear in an NA or FI car can have huge benefits.

 

I would agree his car is fast as *****, but as for I guess most end users even reaching his numbers seem out of the reach of most. I would say gears wouldn't be the best idea for someone who isn't a solid veteran running a heavily forced induced car or they will inherit the spin fest, hell most of the guys with 350Z's I used to hang out with couldn't even handle their cars with bolt ons.

I can only chime in on what I've seen around the forums as for me I know I'm definitely not the best dragger, on my DE 350Z the best I could ever pull was a 13.8 so high it was almost a 13.9 with a flat 2.0 60 foot. I'm not even gonna use the AZ is hot excuse. :laugh:

 

Very nice posts guys, haven't read posts so good in a while

Keep us posted NBS

 

Lol, I just want to see somebody put the gears in already! So, let me get this straight, I can use a G35 pumpkin and just put the new gear in that and just do a complete swap? I don't want to take my stock pumpkin apart and want to keep it whole for warranty purposes.

Also, my last question would be, if I can, and do use a G35/350z rear diff, is the LSD the same that's in my G37? I would hate to go to an inferior lsd just to use a different gear set.

 

I don't think the key part is a G35 housing. I think the right part is the "6sp manual" housing. I don't know why this is but they are slightly different. The 6sp mt housing is slightly bigger and the 4.08's fit in it. The axles and everything else will work with both housings so I don't think you have to swap anything else out. Now, here comes the tricky part... The stock limited slip is crap to begin with and only degrades with time. This is not my opinion, this is the opinion of a lot of guys on that other forum that have been using this differential for a number of years. The stock limited slip will work with the gear swap but it's kind of a downer if you ask me. Spend money to do the gears right and you still end up with a differential that should have been upgraded.

The good diffs are over a grand just to get started.

 

I may be lost here...
My comparison of 6MT vs. 7AT suggests that the 6MT with 4.08's is still "taller" or "higher" than stock 7AT gearing?
7AT 1st 4.92 axle 3.36 = ~16.53 Total drive line gear reduction
6MT 1st 3.79 axle 4.08 = ~15.46 Total drive line gear reduction
If so, I'd think the lower gears would be a significant plus in the 60' times for a 6MT given good traction.
-Can't wait to see some real world numbers!

 

This is going to be a shot in the dark - so please dont flame.
would this work for the AWD models?
If this would be possible on the X models - it would eliminate the wheel spin that people seem to experience with this mod.

 

No. Not unless you could figure out how to change the front as well.


Has anyone heard that if you do this gear swap with an automatic, that you loose cruise control?

 

According to a post by Z1 on the 370 site, it looks like you lose cruise control on automatics, not sure of the reason why but you do. Cruise control is still maintained after the swap on the 6MT.

 

Anyone get to doing this?