About a couple of weeks ago I purchased a pumpkin with a 350EVO 3.9FD & oem VLSD installed (actually it was a used setup that had around 5000 miles on it + the final drive gear was installed in the pumpkin by 350EVO). Yesterday I got around to installing this on to my car. Here are my impressions:

1)Performance:
All I have to say is WOW. F*cking WOW. The reason why I went with the 3.9 instead of the 3.5 or the 3.7 is because I wanted performance you can feel and this is exactly what I received. Going from a 3.3VLSD to a 3.9VLSD made quite a noticeable difference in the feel and response of my 5AT (actually more than I expected). The response of the car has improved dramatically and it has made an improvement throughout the rev range. I fly through 1st, 2nd, and 3rd. With the 3.3VLSD it felt like it was taking too long to get to the meaty part of the powerband, especially after my osiris reflash with the 7200 rpm limit. The 3.9FD took care of this. WOT in 1st & 2nd gives me a lot of wheelspin . Rolling on the throttle in 2nd will break the tires loose (and will get the rear light). The car accelerates harder in every gear. There is one onramp where I go WOT (with the 3.3FD) from 1st-3rd and I am able to hit 90 before merging on the highway. Now on the same road I am hitting 95-97 (@7200 rpm in 3rd) before merging on the highway. I am going to the track next friday to see if I can quantify the improvement .

This is by far the best mod I have done to this car. I'll probably go with the 4.08's after I go with a more aggressive set of cams. IMO this will be the perfect mod for any 5AT VQHR motor.

2)Streetability:
I know some of you had some reservations about with a 3.9FD in the 5AT but believe me this setup is VERY STREETABLE. It never feels like I am always revving out the car. It feels like a more responsive 5AT G35. This mod makes city driving much more enjoyable and I can get around cars on the highway a lot easier without downshifting. With the 3.3FD the car was dull at low revs and I would have to either downshift or add a lot more gas to speed up or to get around cars. Now I can increase my speed at low revs with a small tap of the gas. This alone will help improve my mpg (less load) in the city as well as save some wear & tear on my car.

As expected my cruise control does not work (the light just blinks when the button is pressed) but I wont be missing it since my right foot does a better job. So far my mpg has gone down only because I can not keep my foot off the gas . I'm expecting my highway mpg to go down slightly but I'm also expecting an improvement in my city mpg. I didn't buy this car to save gas. When the converter locks the rpms are higher than before (80 is @ 3300-3400 rpm) however its not really bothersome and I'll take the tradeoff for the performance. I also have a slight whine when crusing at a steady speed. I did some research on this subject and I found out that this is because the pumpkin was setup with a little more offset (looser backlash) with the shims. This was intentionally set up this way by 350EVO since it allows for cooler operation of the diff. In a nutshell, the looser (more offset) the gear has, the cooler it runs, but adds to the chance of a rearend whine and the tighter (less offset), the hotter it runs, but lessens the chance of gear whine. The whine is only present when I give it steady throttle and it disappears when I let off or when I go WOT.

Sorry for the long post but I wanted to give a detailed review for anyone thinking about this for their 5AT.

 

pshhhhh my car doesn't even have cruise control. Glad you enjoy the 3.5 drive, now I'm seriously considering it myself.

 

I dont have the 3.5 FD I have the 3.9FD on my 5AT . Believe me it is worth it.

 

lol sorry misquote, I meant 3.9FD. I wouldn't get the 3.5 either. Time to save up.

 

need to start saving, about how much will this cost me?

 

The pumpkin will need a rebuild & you will need a 6MT rear diff. 1500-1800 sounds about right for an AT(depending on what parts you go with). If you already have an 6MT subtract the cost of the diff from that.

 

damn ive been reading alot into this mod... I go to the track alot, i mean alot, and i want something to beat the damn srt-4's.I run 8.8-9.0 in the 1/8th, they r bout 8.4-8.8.....
I was thinking of going with the 4.08 gears. arent they a nissan frontier stock item and go for only 500 bucks brand new... Why wouldnt you go with this route? it is cheaper and a little more performance accleration wise isnt it?

 

Your 1/8 time & trap would definitely improve and it will help to get the heavy G coupe moving a little easier. I bought the pumpkin with the 3.9FD already installed so I had no incentive to go with the 4.08's. However, that may change after I get a more aggressive set of cams.

 

4.08 is what I want to go with also. Im just worried about traction with street tires. I already have 285's on the rear and I can totally break them loose in first and second with just the stock gear. Im sure with the 4.08 it will be SPINNNN city!!

 

yeah i had 295/30/19 and was spinning all through 1st and 2nd at WOT, now im running stock 18's 245/45 in rear. spun like crazy last time at track but it was 45 outside, too cold for great traction anyways....im going tomorrow and it going to be 65-70 out so maybe ill get way better traction....and get into the mid 8's..

btw, you said you would take to track? have you been already... what were you running and trapping... ive only run the 1/8th and my best is 8.801 and best trap is 82.4 mph... best 60' is 2.001.. i want a sub 2 so bad

 

At the track I'm running at now my best time has been a 14.2@100 b/c of elevation & DA. At sea level I usually run 13.7-13.8 @ 102-103.

 

stock? besides gears

 

I ran those times with:
ZTube/Spacer/Headers/Test Pipes/Exhaust/Cams

 

Great write-up. Im seriously thinking about getting one of these things.

 

tighter gears and an LSD is the best thing ive done to my car ...well..one of the only things but you know what i mean ^^

 

It's too bad no one has come up with a fix that allows you still use the cruise control. There has to be a way to do it.

 

do you need to reflash it with osyris or techno square after install? how hard is it to install it? do you think you might burn out your differential if applying to much force to it?

 

Yeah I know



A reflash is not necessary however if you race the 1/4 often it would be helpful since it will allow you to hold the gears longer. It wasn't hard to install. All I had to do was unbolt the old pumpkin & bolt the new one on (the new pumpkin had the FD already installed). However, you will need to get rebuild if you want to have the 3.9FD installed. Depending on the shop you take it to it can take from 5-8 hours. IIRC the only way you can burn out a diff is from improper installation or from too much power.

 

nice thinking of going with the 4.08 myself.

 

I just got mine in my 6mt HR...but ive only driven it 4 miles back from the shop...have to work 7 days in a row and its not the car I drive to work

Looking forward to my first day off though!