Final Gears for the FX?

Steeper is taller gear, even if a RWD FX puts in a 3.5FD from a 6MT we still have a taller gear due to the tire size. AWD is a 3.7FD on the 35 and 45, this helps with moving the heavier vehicles faster.

5AT FX with 3.7 might be closer to the 5AT G35 overall, 5AT FX with 3.9 is closer to the 6MT G35 overall.

Mpgs suffer a bit and you lose the very top end of the max speed. The FX will downshift less often, and the speed limiter is at 135/145 or something anyways. I forget which one of those is the speed limiter.
 
Diff has magnet sensors on the output shafts that measure revolutions, this and the wheel sensor are what give you a speedo reading. As long as tire size doesn't change you should be fine. 6MT guys have a speed sensor on the trans that's a little different than thr turbine revolution sensor for the 5ATs. I've heard some 6MT guys have speedo issues when changing.
 
There is a difference between a 3.3 open/vlsd, and 3.5/3.7/3.9/4.08 open/vlsd.

That's what that comment means. whatever LSD that is it is made not made for the 3.3 ring and pinion.

You can drop a AWD FX pumkin right in a have factory shimmed 3.7FD. Downside is I don't think any FX diff is a viscous LSD, all are gonna be open is my thought.
 
^^^

I need to do more research, because I was a little lost with the LSD.

So we should change the LSD to vLSD?

I guess we cant just pick up a Central20 fd and have it installed?

come on V, make it easy for me and others (Will), what do we need in parts

anyways, I probably will be doing this in the future so I have some time to educate myself...thanks for all your help
 
Easiest simplest and most cost effective way to change the RWD FD is to get an AWD pumpkin. Installing a final drive is semi expensive, you end up changing out seals and bearings and xx.

Unless you find a G/Z pumpkin already upgraded to a 3.7/3.9/4.08 upgrading the RWD 3.3 pumpkin can get expensive. To use a G/Z pumpkin, swap out companion flanges (drifeshaft mating piece) and diff cover (fx hanger bolt is larger) LSD is cool, don't get me wrong. It's gonna be up to you if you want to have an aftermarket LSD or not.
 
Are these the things where you put them in and all of a sudden the rear wheels are really easy to spin? I swear I saw a video from some guy after and install, and he was just doing donuts and spinning the tires all over the place.

---------- Post added at 09:24 PM ---------- Previous post was at 09:22 PM ----------

Here's the video, wouldn't mind being able to do this :wink:
YouTube- 350z with NISMO L.S.D. trying some drift
 
LSDs are good for that. hahhaha, allows better control and predictability about what both inside/outside drive wheels are going to do. If you look at my old old donut video, you can see not both wheels are spinning evenly.
 
we did a cusco dif in a Z & it chatters on turns at low speeds pretty bad... is this something to expect or are some better than others? I think his is set to 80% lock from what the seller said...
 
Cusco is one of the quieter ones. Tire/wheel chatter? Or actual LSD noises? The more aggressive the diff and engagement the louder the tires go clunk clunk on low speed turns.

OS Giken probably the quietest with positive engagement.
 
yeah, clunk clunk, guess it didn't help that we used aluminum bushings to mount it too, that would drive me nuts on the fx though I think, if you didn't know better it almost sounds like somethings broken... clunk clunk clunk... at speeds more than 10-15mph it's fine though, only on slower parking type manuevers really...
 
reviving a thread from the dead:
I can see how in the common tuner world, taller gear swaps are the attractive way to go, but I'm think from the opposite spectrum. Has anyone attemped the shorter 5 gear? Crazy and unpopular, I know. At freeway speeds, I like nice RPM's (~2300) at ~65mph. MPG is prime at this cruising speed. Then at ~75-80mph, RPM's are maybe 3200-3400 and MPG is in the toilet. It would be nice if 5 gear could be swaped shorter and a nice healthy MPG can be achieved cruising at 80-85mph. It would be okay to lug 5th a little bit in the 60's because manual 4th is excellent in the 60's and 70's (I think I take 4th up in the 90's without getting close to redline).
How can I get lower RPM's at 80mph?

(Of course I would never think of exceeding any posted speed limits. This would only be taked full advantage of on highways with high speed limits.)
 
Changing the final drive ratio will affect your fuel economy as well. If you do change your final drive from 3.3 to 3.9, you will have a better acceleration in speed and in how quick your fuel gauge moves to empty.:eek.:
 
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Yes, but is I were to switch 5 gear only from 3.7 (AWD) to 3.5, would it be easy enough (or even possible) to retain the quickness and same mpg for gears 1-4 and have a slower but higher top speed for 5th? Keep in mind that high end top speed really doesn't matter to me, but lower RPM mid range in 5th only is what I'm after.
 
porkandbeans said:
Yes, but is I were to switch 5 gear only from 3.7 (AWD) to 3.5, would it be easy enough (or even possible) to retain the quickness and same mpg for gears 1-4 and have a slower but higher top speed for 5th? Keep in mind that high end top speed really doesn't matter to me, but lower RPM mid range in 5th only is what I'm after.
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If I am understanding correctly, you want to only change the 5th gear ratio while leaving the other gears the same. That will be an expensive project on top of the axle swap. I would just swap the VK engine for an VQ engine that can be supercharged/turboed for the kind of money you will be spending on that speed project. The blown VQ will probably give you the level of torque you want to feel and give better gas milage than an transmission/axle swap. P.S. I was thinking about doing that when I read how much power a blown VQ makes using a Stillen supercharger. Plus a used VQ engine costs only about 2k vs. 4k for a used VK engine, if you can find a used VK engine at all.
http://www.youtube.com/watch?v=8fbIC3MdutQ&feature=player_detailpage- an extra 110 hp to the crank puts the FX35 in the FX50S territory!!
 
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carguy75 said:
If I am understanding correctly, you want to only change the 5th gear ratio while leaving the other gears the same. That will be an expensive project on top of the axle swap. I would just swap the VK engine for an VQ engine that can be supercharged/turboed for the kind of money you will be spending on that speed project. The blown VQ will probably give you the level of torque you want to feel and give better gas milage than an transmission/axle swap. P.S. I was thinking about doing that when I read how much power a blown VQ makes using a Stillen supercharger. Plus a used VQ engine costs only about 2k vs. 4k for a used VK engine, if you can find a used VK engine at all.
http://www.youtube.com/watch?v=8fbIC3MdutQ&feature=player_detailpage- an extra 110 hp to the crank puts the FX35 in the FX50S territory!!
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Yes, I was wondering of a 5th gear could be swapped easily. I was hoping that by rebuilding the pumpkin (or 2 in the case of AWD), that an easy parts swap would change the RPM range of 5th only while keeping 1-4 stock. Just a random dream I guess.
Neither a motor swap or FI would interest me.
Are there any ECU adjustments that would make 5th gear cruise at high speeds and modest RPM's?
 
porkandbeans said:
Yes, I was wondering of a 5th gear could be swapped easily. I was hoping that by rebuilding the pumpkin (or 2 in the case of AWD), that an easy parts swap would change the RPM range of 5th only while keeping 1-4 stock. Just a random dream I guess.
Neither a motor swap or FI would interest me.
Are there any ECU adjustments that would make 5th gear cruise at high speeds and modest RPM's?
Click to expand...

I believe it could be done with the right mechanic and the right amount of money. The parts are available at the dealerships, and probably some junk yards. A transmission shop should be able to modify your transmission's gear ratio. So your dream could still be a reality, i just hope your wallet can keep up.:wink:
 
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