I want to upgrade my FD, i was looking at these http://www.z1auto.com/prodmore.asp?m...ne&prodid=2833 which are the 4.08 gears.

I was wondering does my car being AWD affect installation, meaning is it possible to do?

I also see people add a differential like Quaife and such. Do you need to add a Differential along with the final drive?

Im just looking for that speed and not the handling.

Thanks everyone.

 

LSD such as Quaife goes inside your stock differential and allows optimum transfer of power between the two wheels on a given axle. Since you have have AWD you have two differentials one in the front and one in the rear, which are given power from a transfer case.

The final drive gear is apart of your stock differential gear which is a ring and pinion gear. To sum it up for you theoretically you would need double of both parts for an AWD car. Not to mention your cruise control and vehicle speed sensor would be thrown off by a change in your differential gear ratio. You would probably need to recalibrate everything through the ECU.

LSD and a differential gear ratio change improve acceleration and handling dramatically. The downside is that your engine works harder and revs higher in every gear once you shorten the differential gear ratio and this will decrease fuel economy. The newer vq35hr models come with a shorter differential gear ratio of 3.7:1 and the vq35de automatics have a 3.35:1 and 3:56:1 for the manuals. Part of the reason why the HR's blow us by in terms of all around characteristics.

Hope this was helpful anyone please correct me if I made any errors.

 

Thanks! very helpful indeed, so your telling me i need to buy two Final Drive gears?

Im not to worry about cruise control unless it conflicts with my osiris tune which uses the cruise control buttons.

So is it a must to have a differential installed when installing your final drive gears? Or is it one of those things that is easier to do if you do it all at once if by any chance in the future you decide to install a differential? In my case it would be two installed

Thanks again.

 

Choosing the right gear ratio is very complicated. Additionally, adding too much gear can negatively impact acceleration. It is quite possible to over-gear a car. Deeper gearing is not necessarily better. The car will certainly feel faster because of the increased torque multiplication, but it might be moving too quickly through the powerband. Seat of the pants acceleration might not jive with the real timed acceleration numbers.

The factory 1st gen gearing is pretty ideal for acceleration, especially in the 1/4 mile. I've verified this using the gear/rear end ratios vs power/rpm, basically an ideal shift point calculation. Not a whole lot can be improve on. With the stock sized tires, the 5AT could use about 3% more gearing and the 6MT about 5%-7% (7% for the Revup). Ideal gear ratios are determined by the powerband and Nissan did a great job selecting good ratios and final drive. The 5AT RWD uses the 3.3 gear and the X and 6MT use the 3.5 gear. The 5AT doesn't need as deep initial gearing as the 6MT because it has a torque converter which greatly increases initial torque.

The only time you really need to increase gearing in the 1st gen car is if you increase the car's ability to make power above 6300rpms. This would basically take at least a set of cams. If you modded you VQ35 to make power to 7200-7300rpms, then a 3.7-3.9 gear would be a good choice. 4.1's if you're really into drag racing.

The VQ35HR uses deeper for the following reasons:

1) It runs .7" taller tires. That additional circumference reduces gearing.
2) The car is 120-150lbs heavier than the 1st gen. It needs the additional torque multiplication to get moving swiftly.
3) It the motor revs to 7500rpms, has a long and wide powerband, and needs the extra gearing to pull through it. The taller 1st gen gears would make the HR labor a bit.

4.08 gears in the X will be total overkill and I'm not certain that AWD will take kindly to the increased ratio. MPGs will be greatly reduced and cruise control will be lost. I don't believe the front gear/pinion are off the same design as the rear so buying two sets of gears probably won't work. Even if the gears could swap in the front, you're looking at probably close to $3K for the work to make your car slower. I suggest taking the money buying some performance parts that actually make the car quicker like the XYZ pipe with resonator, plenum spacer, HFCs, and lightweight rims. If you want a little more gearing for the strip or road course, simply buy a set of cheap 17" rims and mount shorter tires. The shorter tires will increase the final drive.

 

Your the man DaveB, you answered everything that was questionable in my head. Sometimes it sucks to have an X, but then again sometimes it doesn't. I never thought the gears in my car were 3.5, i thought they were 3.3.

I plan on getting all the mods you mentioned above and as well as the Shockwave exhaust for the sedan when it comes out.

Thanks again.

 

On an 03 6MT coupe, about how much of a HP/TQ increase would you get from adding the parts you listed?

 

this is an old thread about gear ratios. Not the correct place to ask about HP increases from breather mods.