VHR + FD Gear Ratio upgrades - 3.9 and 4.08

Ivoidwarranty

What would it take to get you to look into the autos? I have a G37 5sp auto that I'd like to do a gear swap in.

Z1Performance

I have a feeling the auto's are just like the Z's, meaning you will need to replace the differential to one from a manual (stock or aftermarket) as well as doing the ring and pinion

javol

Yes, it is the same.

I got an used diff from a manual 350Z and installed the 4.08 set up.

Now, my 370Z 7AT is incredible in the sequence "1st-2nd-3rd gear" .

Very very very short gears and quick shifts.

Note: i added the sprint booster to the throttle, other great modification if you like to drag the 7AT car !

Ivoidwarranty

Thanks for the info on the gears. Now I have to make a post on that sprint booster (not a fan).

Zsteve

I like to get up and go and have been thinking about upgrading to a LSD and changing the gears. How does the new gears do for normal daily driving too?

If I put in as lsd do I still need the diff from a manual? Thanks.

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2010 LS3 C6 Silver coupe corvette

javol

Yes, the pumpkin of the manual car is necessary.

You can buy a "good used 350Z dif" for 400 $.

For what concern normal daily driving it is so subjective...

I'm a big fan of short gears, I prefer acceleration respect to top speed.

With a 4.08 set up on a 7AT 370Z, the 250 km/h speed limit and the 7400 RPM limit - in 7th gear - are very close each other. So you can imagine the situation with a bit of fantasy...

THE GOOD: the car feels like a toy.... The way it "eats" gears is very exciting to me... And it is true both in the street (1st-2nd-3rd = fantastic ) and in the highway (5th-6th-7th is fantastic too...). 250 km/h are enough for me...

THE BAD: the car burns more gas, exhaust noise can be boring on the highway, especially if you have an aftermarket exhaust... the jump between 4th and 5th gear is still there, the 4.08 set up clearly does NOT remove it... and the engine oil temperature issue is even more critical than stock...

But at the end: i'm very happy with the 4.08 set up

I got my Z to feel it, to live it...

And during the week ends - with my family - it is still very confortable to drive our Murano on the highway @ 120 km/h and 2000 RPM

Z eliminator

Just wait till you take it down the 1/4 mile. I just got my rims and drag radials. Get a cobb and raise the limiter to 8100 and set the speedlimiter to 280. This way you can dyno in 5th gear. My gas milage dropped from 7.7 L and went up to 9.2 L per 100 km/
36.7 mpg to 30.7 mpg. Rpm at 100 km was 2150, now it 2750.
Is it worth it " Best mod i did".
Soon to be the first N/A to go into the low 12.6's.

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12.343 @114.14 . 4.5 stroker motor is now being built. Dec 1 2015.

racerxj17

Did it throw off the speedometer? I thought I read that it's off transmission input speed... Or front wheel speed.... So the gears wouldn't effect the speedo.

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2009 PW Sport/Touring/Nav M6
Stillen Gen 3 Intake/CBE/Berk HFC/BC BR Coil over/Phillips 6500k/Hotchkis Sways/Stillen oil cooler/B&M SS

Z eliminator

No the speed is taken from out side the Differental. Your cruise control will not work.

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12.343 @114.14 . 4.5 stroker motor is now being built. Dec 1 2015.

CBRich

Come again with the cruise control statement. Is that just the autos doing the switch? I can't imagine a simple gear change killing cruise.

Z eliminator

It did it on my 350z 5 AT and it the same thing is happening on my 370 7 AT.

__________________
12.343 @114.14 . 4.5 stroker motor is now being built. Dec 1 2015.

Ivoidwarranty

Can someone else verify this? I don't see why a gear swap would kill the cruise control?

Z1Performance

the speedometer has nothing to do with the final drive, so it is unaffected

if the car is an auto, cruise will no longer work

CBRich

Understand, swapping the ratio on a manual will not affect cruise control.

Ivoidwarranty

Why does cruise no longer work on the autos?