Has anyone attempted this combo? I've searched multiple forums, and come up empty. Done a little reading up recently on the final drives, and it got me really thinking about it.

There are a few high-hp TT's trying the 3.3 and liking that. I don't think the Stillen S/C (even in stage 4 form) is putting out enough hp/tq to warrant the change in gear ratios.

I know the 3.9 is great for N/A cars, increasing acceleration by 10% or so. I'm actually thinking that the 3.9 might complement the Stillen stage 4, since this kit makes most of its power in the low-mid range. Of course traction is a limiting factor, and why it wouldn't make sense to put on any of the Turbo kits, or even a modded Vortech kit.

But for my application,would it make sense? Discuss. Thanks

 

actually it works just fine with a vortech as long as you have a decent tire setup and stay around 400-420whp or less


IMO it might he harder to initially hook the tires with the 3.9 and stillen because of how much low end torque is on tap with the stillen

 

would you say it's like not having 6th gear on a stock final drive car?

 

no it's like 1/3 of the way of not having 6th - if that makes sense.

from a stop though and in any given gear, the 3.9 will accellerate you into the higher rpms faster where the vortech makes most of its boost. So for instance instead of being at the same mph @ 5300 rpms making 10 psi, I'd be at almost 5900 rpms making 11 psi. The downside is possibly more shifting in some cases

My car is running something around 450-460whp on a dynojet currently and a couple months ago I was having some slight trouble hooking 2nd gear in 50 degree weather. I've since done a few adjustments and mods and think it will hook in 2nd now. I'm running 295 pirelli corsa tires, nismo LSD, solid rear diff bushings, solid motor mounts, and JIC camber and traction rods (stiffer bushings). The stiffer bushings help fight wheel hop for more consistent traction off the line.

I think I do have a problem getting traction in 1st gear, but think I'd probably have trouble even with the 3.5 final drive, so I might as well maximize the rest of my gears for more accelleration

The 3.9 might work well with the stillen - I dunno, you won't know until you try. I don't think the turbo setups like it as much because the tq comes on so hard so fast that it's already difficult to manage the throttle to maintain traction. The 3.9 would just make it more of a bear to do on those cars. The stillen though would have a consistent tq curve across the board and linear response. The more I think about it, the more I think it'd work - ONLY if you get some serious tires though

 

I've been running all these thoughts through my head, but I still haven't come to my own conclusion yet.

It will definitely require shifting more often, but I can handle that.

I'm just running stock VLSD, and no plans to change out motor mounts, bushings, or any rods. Running 285 in the back, although I'm considering going back down to 19's and fitting some 295/30 in the rear.

With the stage 4, the backend already gets reaaally loose in 1st/2nd, so I'm just trying to figure out how much the problem will be compounded

It's a pretty damn expensive mod to try out without being pretty sure, so I definitely can't just jump into it.


Really hoping there are people out there running the combo I'm inquiring about specifically. Hoping for more technical discussion from some knowledgeable guys (regardless of their own setup) as well...

 

The Vortech and the Stillen are almost like opasits in throttle response feel (I have them both). The Stillen has great low end grunt then not much on the upper end, and the Vortech has nicer high end power with a greatly lacking low end.


Like I told you over on G35Driver, ...................


I thought about this idea for about a minute or two before I came to realize why I would pass on this idea. I already have a Stillen SC'ed G and a 3.9 FD rear end sitting in my Z. When my Z's motor was pulled I thought about trying out the 3.9 diff in the Stillen SC'ed G. I quickly came to the conclusion that..........
A) The Stillen (for what it is) has plenty of low to mid range torque and great throttle response.
B) The 3.9 FD is good for helping out underpowered NA cars and great for a centrifugal type SC (like the Vortech and Pro Charger, etc.) that are heavily lacking in low end torque and throttle response.
But, the mating of the two Stillen SC and 3.9 FD) would be not too beneficial at all, not to mention a waste of money that could be spent towards other mods I would see more benefit in a 3.3 gear change than a 3.9.

 

3.9 + Stillen power levels sounds good. You can easily put down that power with good camber and decent tires...

 

Im at 425whp with my Vortech and I have a 3.5 rear with a AT5 . I have no traction at all in 1st and 2nd . I cant go over 1/3 throttle in both gears with out lighting up the tires . Im just running 275's out back , but I dont believe wider tires will help all that much at all . I switched bad last weekend to a 3.3 rear end . Im sure it will work a little better .
The 3.9 rear maybe be good for 375whp or less , but anything more would be a hassle IMPO

 

Seeing as how I havent seen a Stillen past 330-340whp and thats pushing it, he should be fine. Booger, what is your rear camber?

 

It has nothing to do with peak whp, it has everything to do with your torque curve. Gearing change is a torque multiplier. If you go from the 3.538 to the 3.917, it would be a similar effect to increasing your torque levels by 8-10% throughout the powerband.

If you're currently having traction problems in 1st and 2nd, 3.917 will only compound it. If you run wide drag radials or similar super sticky rubber with low camber, so you get it to hook, the car will shoot like a rocket. But that's your only option.

 

I think the tire compound has a lot to do with traction too obviously. If I recall, Booger you're running nitto 555's which aren't known in race circles as being a really sticky tire.

IMO going to more aggressive gearing is partly to get you into the upper powerband faster - where the vortech in my case makes it's power. The stillen shines the most down low and does an ok job up high.

 

Im running stock spec camber . Im sure a better , stickier tire would help some . But with the ease that the tires break loose and with the little amount of gas it takes to do it . Wider , stickier tires will not help enough . Going back to the 3.3 will be a much better salution . I cant amagine what a 3.7 rear [ equal to a 3.9 for a 6MT ] would be like . I would think even 3rd gear would break loose in most of the rpm range .

 

well I can only talk from my experience with my car, but I absolutely have 100% traction in my 3rd gear with my 3.9, and I'd be willing to bet money on a normal 75+ degree day, I'd have full traction in 2nd. When it was 50 degrees with what turned out to be a little over -3.5 degrees camber I would lose traction around 5500 rpms. The 6 speed's 1st gear is just way too short to expect traction without drag radials. I'm in MUCH better shape now with -1.6 degrees camber and all the other stuff I've done - and it's not as cold outside

 

WHen its cool out , air and street . I can get the car sideways cruising at 35-40 in 3rd and punching it . But it will not happen in the summer . Warm summer days are no difference for 1st and 2nd though .

 

if this means anything, when I switched from my 295 ps2's in the rear to my pirelli corsa competition tires, I noticed an immediate difference in traction - and my corsas I've come to find out were almost 2 years old (tirerack refunded me some money because of that)

I was able to get a little more aggressive with launches. I dunno, I think the tire compound makes a pretty good difference.

Another example was when I was running the stock tires when I was running my NA mods (3.9, cams, crawford package, exhaust, tilton, UR pulley, etc ) I'd lose traction at the top of first gear. As soon as I switched to the 295 PS2's, that never happened again.

I dunno, obviously I seem to have more traction. I never drive my car when it's below 35-40 degrees though so I don't know if you're driving in colder temps than me. My 3rd gear is a little over 13% more aggressive than the auto's 3rd gear with the 3.5 final drive.

I already mentioned the other things I've done to my car for traction and I really do think they add up to biting down the rear down more. I can switch to a less aggressive final drive like the 3.5 and I might be able to give it more throttle in 1st gear, but that'll be it. The rest of the gears would be slower.

It seems the higher powered vortechs with 6MT and stock final drives shifts into 5th anyway in the 1/4 mile, so I doubt I'd be able to stay in 4th. I'm not running drag radials or slicks, but I suspect if I were to I'd fully hook 1st gear up and then have the 3.9FD's more aggressive gearing for the rest of the 1/4 mile with the same number of shifts

However I'm not sure if running my setup with slicks would be good on the axles given that other people seem to break the axles a lot - even the stage 5 ones.


I have thought about changing the gear ratios and going with the 3.5 final drive with ATS LSD. I'd want straight cut gears 1-3, the rest helical. I have the gear ratios figured out and they'd be suited a little better for the vortech - and possibly finish the 1/4 mile at the top of 4th gear. $5-6k is a lot to swallow for just a transmission though...I'm kinda inclined to wait and see if someone comes out with a conversion kit for a T56 or something

 

Again, I really don't think the Stillen kit justifies going to a 3.3. Wish I was a baller so I could just throw it in to find out for sure, give everyone a thorough review, and then decide to keep it or toss it. Still crossing my fingers that someobdy out there has tried this exact setup, and will pipe in with some real world experience (although the discussion thus far has been good, too).

 

I would only consider the 3.3 FD if you really are having traction problems and can't really move into a stickier tire, but even then chances are 1st or maybe 2nd gear are the only gears giving you trouble with traction. Once those gears are over with, you'd be stuck with slower accelleration in the rest of the gears. It might be a toss up in the end.

The 3.9 would make traction worse, but if you can manage to get traction at WOT, then it'd probably overall help you for most types of driving. The key is to balance your gear torque with your engine torque with the type of tire and traction you're able to get

 

Just found out over the weekend, that there's also a 3.7 available from Performance Nissan. Apparently it's an OEM part, but I don't know exactly which model it's coming out of. Any thoughts on the 3.7, or would the differences by negligible?