the 350EVO 3.9 final drives will be arriving very shortly. We are expecting them the week of July 19th.
Cheers
BJ@350EVO.com

 

Sorry, I'm not positive what the significance is here, but...

I assume the stock final drive is taller than 3.90. So, installation of said shorter 3.90 final drive will provide faster acceleration in every gear, correct? Will such an installation cause any problems with the VDC, odometer, or other systems? Thanks.

'03 G35s 5AT, Garnet Fire/Willow
Staggered 18" SSR GT1/Bridgestone PP S03
Eibach Springs/Sways, Stillen 2-pc BBK
Stillen Intake & SS Cat-Back Dual Exhaust

 

the wheel speed is taken from the wheel speed sensors on the two front wheels and on the inner drive flanges of the axles. Therefore it will not and does not effect the speedo, VDC or crusie control.
YEs this will aloow for faste acceleration throught the gears and is ideal for trackng or autoXing the G35 or jsut more smiles. It is by far one of the best mods that you can actually feel in the drivers seat.
BJ@350EVo.com

 

Is this for auto and manual? How much better acceleration can you also expect out of this? Also how much will it be. Thanks, Martin


Martin
2003.5 BS G35
Nismo Aero/Sport Package
Injen CAI
B+G Springs
ADR M-Classic 19's..

 

1) You get better acceleration through shorter gear ratio.

2) You get worse gas milage, since the engine rpm will be higher at the same speed.

3) You know have to shift to 3rd gear to hit 60mph?

4) You might void the powertran warranty if the dealership is picky.


I know for older E36 Bimmers the final drive ratio makes a big improvement in acceleration. I am not sure if this would be very beneficial to the G35, since we have 6 close ratio gears, and the acceleration in the first 3 gears are already very good.

 

This is great improvement if you are tracking your G35. Gas mileage wont suffer that much. It doesnt efect your speedo. And the dealership would prob never even know its in there. The only way tehy would be able to tell really is to remove the diff and count the teeth themselves.
its the best modification that you can actually feel for the money.
Retail is
$899.95
but we will be doing a package deal with a LS diff....most likley nismo diff.

 

What is the new top speed with this rear gear?

SCZ on my350z.com
2004 G35 Coupe 6MT | OB/Black
Premium | Aero | Splash Guards | XM
Z Tube | Pop Charger
Helix Test Pipes
Unorthodox Crank Pulley
Injen SES

 

I will have to check back at work...We baised it apon getting the rev limiter raised to about 7200 RPM ....I wanna say about 168....but have to check

 

Wouldn't a lower gear ratio (higher overall numeric value) cause the car to have a lower overall top speed? Not that I ever plan to get the car to those speeds anyhow.

 

I would be interested in knowing how to increase the rev limiter to 7200rpm safely. Would I need to strengthen the internals or buy new rods/pistons? One thing about the VQ35 is that it kind of becomes melow over 6500rpm. You don't get the high rpm umph you do on 4 bangers.

 

gdup,

it's the other way around.

Autos have a 3.358 FDR, while manuals have a 3.53x final drive ratio. SO, by putting this 3.91 FDR on an AT car, you will changing your overall gear ratio by 16.4%, while with an MT car the change is 10.8%.

So you guys be the judge.

 

350EVo

I have already replaced by diff with the MT Z's 3.53x diff (the entire assembly). And I most definitely and consistently have cruise control problems. Most of the time (~70%), if after starting the car i accelerate quickly through the rpm band (while CC is engaged OR NOT), cruise control refuses to work. Upon trying to engage it, the "cruise" light will come on, but the "set" ligh will blink quickly, and of course CC will NOT engage.

DOn't know if this is specific to automatics, open-diff cars, or the drive ratio itself, but i am leaning toward the very latter, as when this happens, a 'pending' code is stored in the ECU, and it points to the "vehicle speed sensor" in one way or another (do not recall the actual Consult II readout).

Please advise

Gurgen

 

O.k. so the stock 6mt has 3.53 gears. Changing the gears to a 3.9 set would make the top speed SLOWER, not faster. I'm 100% positive that is how it works, not the other way around. (The engine will be at higher rpm's to achieve the same speed).

I have to admit, that is not much of a change for the 6mt. I had a Camaro with 3.53's and replaced them with 4.10's. I was still able to achieve well over 160 mph in 6th gear.

 

gdupg35's right... the steeper gear ratio will most definitely reduce top speed.
In terms of the G's 1/4 mile performance, the 3.9 final drive would give a slightly better E.T. (i.e. acceleration) but with a slightly lower trap speed.

A general rule of thumb: with a final drive steepened by one gear step (say from 3.53:1 to 4.53:1) you can expect about a tenth of a second better 1/4 mile ET and about a 1 mph reduction of trap speed.

Although the car's top speed will be lower, the engine speed should be higher across the board (so higher rpm's at any given speed), and of course the mileage should be lower.

Same thing goes for wheel circumference -- smaller wheel equals better acceleration, lower top speed and lower mileage. In fact, you could think of your rear wheel as being your actual "final drive".

 

Might your general rule be a little too conservative?
Based on a 10% torque multiplication: acceleration should increase by the cube root roughly 2.2% of say 14.5 secs......I calculate roughly 0.3 seconds less whatever might be lost if an extra shift is required. Based on 220 Rw lb/ft

That is always the rub, setting up gears so that the quarter mile is exactly completed at the highest overall torque multiplication at redline........of course depending on the closeness of gear ratio spans.

Even the AT is optimized [with a 3.357] .......[4.938 total in 3rd gear]........hitting redline at ~~98-100 mph. A 3.538 [3.54] diff gear would force a shift right before the timing light maybe using up all the gains and more in shift time delay.........now with a 7200 rpm rev limiter you could make it.

Lot of trouble and expense for 0.1-0.25 seconds.

How are members AT G35 running the quarter - locked to 3rd gear max and hitting rev limiter just after lights?