OK, so which of you guys has 4.08 gears and likes them for road courses?

clintfocus

i thought about it, but locally at the socal tracks, with my 18s im at the top of gears before brake zones, so i dont wanna start being in between gears with the 4.08s

DEpointfive0

And if your overall diameter is already smaller, you've geared up the car anyways.


If you want to gear up, maybe 3.9's?

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GSS138

Good point. Will think about that at Button Willow this weekend and see how often I am revved out before the end of a straight. I figured 4.08 would be good on tracks like Big Willow, and probably AAA, would force a shift on the long straight after the hairpin, but might be better coming back onto the main straight after the esses.

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GSS138

Does someone make a 3.9?

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DEpointfive0

Tomei

Tomei 3.90 Final Drive Gear Set


$150 more than Nissan's

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GSS138

Hrrrrrrmmmmmm. That is interesting indeed.

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SPOHN

For the track I go to the most any different gearing would hurt me but in some cases it would help. It's a toss up.

For the LSD you ordered the back lash needs to be set perfect or it will make some racket and end up having a shorter life.

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martin82

for socal tracks new gears are not needed, the Z makes enough power

DEpointfive0

Go away, you're putting a supercharger on your car, lol



You should swap diffs with me :-)

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GSS138

I agree with DE, your argument holds no weight martin. Anyone removing stillen g3's is putting a Supa Chaza on. Whether they want to admit it on facebook or not. Pretty much the last person that should be arguing the Z has enough power. :P

I agree with your decision to do so though. Street is a dumb class for us. there is too much of a difference between entry street and the top of street. Since your suspension is still tuning in, why not tune it with more HP. That's why I am doing breather and drivetrain mods before suspension.

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DEpointfive0

^I win

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martin82

No idea where you guys get the idea to upgrade gears first lol.

GSS138

Drag racing videos.

So Ru going to make it out Sunday?
DE Heading to Button Willow Sunday, but leaving Sat any interest in going up?

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DEpointfive0

Saturday night there's a meet, and Sunday I'll be at work ;-(

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BGTV8

You are running a 6MT and if you are a track junkie, then the answer to your question is based on whether you are likely run out of rev's in 6th at any track you currently visit.

I have attached copy of my gear ratio/speed sheet based on several tyre diameters so you can play with the options, BUT I reckon our Phillip Island circuit is going to match most of the high terminal speed circuits available in the US, and I don;t use 6th at PI and still don;t run out of revs heading into T1 which has a downhill approach, AND I am using 18" wheels with "little" 275/35R18 rear tyres (overall diameter about 650mm). I have a set of 265/35R18 to try next (I have gone square on this tyre recently, having used 265 on the front and 275 on the rear previously).

Now with 4.08 gears and my tyres, my Vmax with the OEM gear-box ratios and my own rev-limit of 7000rpm (as I do not trust the OEM oil-pump at sustained high revs) in 5th falls to 210kph and 6th is still 264kph, so I reckon that drag above 210kph is still going to affect the engines ability to continue accelerating the car a whole lot more. My car seems to be drag-limited at around 235-240kph as that is the best Vmax I have ever logged at PI (and that was with a 30kph following wind).

If I had more torque (SC or TT), then I would certainly go for it.

If you remain NA, then there will be some benefit for sure as in the lower gears the torque multiplication effect will be greater and for a given amount of torque, the engine will accelerate the car more quickly, so you WILL see gains, but I am not sure how significant.

Use the XLS to check your corner entry speeds with old and new diff ratio and establish whether your gear shift points will be radically out of phase with the way you currently drive your tracks, and make a decision based on that.

NOTE: The XLS is embedded in the DOC file attached as the forum would not let me upload an Excel sheet. Enter your tyre size in the boxes on the top row and it will re-calculate. I know that the rolling radius is a little less than that which the sheet calculates so you can adjust that if you like, and I also know that not all tyres respect the sizing but this will give you a reasonable idea at least).

RB

Attached Files

Z34 Speed in Gears.doc (44.5 KB, 6 views)