Im looking to upgrade my rear differential gearing to 3.5 or 3.69. i have a 2003 g35 sedan just purchased a vlsd, becuase i have a open diff. i also have a 3200 rpm high stall torque converter. i want an extra extra ennffff when i punch it. How do i go about getting my gearing changed.

 

It's far easier and cheaper to go find a pumpkin with the 3.54 or 3.69 gear sets and swap them in rather than actually pulling out the old gear and pinion. I did my 3.54 vlsd swap in my driveway in about 3 hours. The pumpkin cost $320 from a local recycler. It's one of my favorite mods. IMO, the 3.54 gear seat is the way to go for daily driving and MPG. The 3.69 gear is a bit aggressive and on your 03, you'll loose cruise control.

 

Out of curiosity, how do you lose cruise control on a final drive change?

 

Yay to Dave for the fast response... I have been wondering about this too!

 

The short version. There are two different points from which the car calculates MPH, the wheel speed sensors on the differential and sensor on the driveshaft. The ECU compares the values, though we believe the true calculation comes from the wheel speed sensors because when you add gears, there's no speedometer error. If you change the gears, the sensor value on the driveshaft doesn't match up with that of the wheel sensors. If the difference becomes too great, the CC thinks there's a problem therefore it won't engage. The 3.69 gears cause this problem, at least in the 03/04 cars.

 

If you go from a 3.3 to a 3.5 then you shouldn't have a problem. Your speedometer will be slightly inaccurate but thats it. As already mentioned, going to a 3.7 may cause problems.

 

Man! Dave is PWNING it with the helpful answers tonite!

+1 on his comments OP, dude knows what he's talking about.

I've been thinking about trying to make an electronic module to "falsify" the VSS pulses to agree with the WSS and see if I could iron out the problems so guys who have swapped to a 3.7 could have their cruise control back... trouble is, I still have the OEM diff, and if I move to a different one, it will be the 3.5, not the 3.7... and I have no one nearby with a 3.7 swap to be my Guenna pig

Actually, the speedometer works off the wheel speed sensor, so it checks speed AFTER the FD ratio. The only thing that will affect the speedometer is changing the overall diameter of your back tires

 

Can this be solved with any sort of tuning software?

 

Which models have the 3.5 with vlsd so i can go find it.

 

i Just found a pumkin with 3.5 gear ratio. is it going to be a big difference. can you guys give me some input on the percetage of the difference in the swap !!!

 

Unfortunately not, but NFSP is on target by trying to develop some sort of module to correct for the issue.

I've read of 6MT owners not being able to engage CC at speeds above 72mph if they've gone with 3.9X gears.

 

All G sedan 6MTs from 04 to 06.
All G 6MT coupes 03 to 07.
All 350Z 6MTs with the Touring or Track package from 03 to 08.

No, it's not going to be a huge night and day difference. It's only like a 7% difference. It's not like going from a stock 3.27 gear in a 97 Cobra to a 4.1+ gear set. You'll notice snappier acceleration in 1st, 2nd, and 3rd gear. The 1 to 2 gear change and acceleration feels much better matched. From a 70mph roll on, it doesn't really feel any quicker.

Having the VLSD is nice because allows you to have a decent more cornering acceleration and it makes the car more consistent on a launch. The 3.5 VLSD pumpkin I got had 65K miles and had worries the VLSD would be cooked because I read so many posts saying the VLSDs get worn out by 60K. My VLSD still operates perfectly. I also know of 3rd gen (89 to 94) Maxima owners with stock VLSDs that still operate fine even after 100K miles. Something tells me the Nissan VLSD must be a little more robust than many other VLSDs on the market.

 

As Dave said, no. Unfortunately, none of the tuning software addresses this issue as of yet, and it's questionable if they EVER will as it's not exactly "performance related"

I don't remember the exact ratios (3.3 and 3.5 are approximations) but yeah, like Dave said, you're looking at a 6 to 7% increase in RPM in any given gear.

So if at XX MPH in 3rd, you're doing 3000 RPM, you'll be right around 3200 RPM at the same speed with a 3.5.

Just multiply RPMs by 1.06 or 1.07 to get an idea of the change.

 

thanks, but what models including the coupe have the 3.5 and the vlsd. My uncle did a skyline conversion. He has the orginal vlsd 2004 g35 coupe A/T diff but i would like to know if it is 3.5 or not because it would be a free upgrade!!!!!!!

 

^ um...