3.3 vs 3.69 Final Drive with FI setup
 

To boosted guys: has anyone here with MT and FI done a final drive change from OEM 3.69 MT to 3.3 AT? How much does that help with e.g. 1/4 mile time? Is that worthy of 0.2-0.4s less for 1/4 mile?

There are a few who have. If their names pop into my head I'll PM them to chime in...

If you WANT to make the switch, I'm more than happy to swap with you!!!

I hope someone done it before and will share with us some results, I know that 1&2 gear traction should be better but would that be a real gain with better time on 1/4? I already have the Racelogic Traction Control, Whiteline bushings, Toyo r888 and looking something more...

Your working against physics. There is only so much traction available at any given time. Changing gear ratios does not change the amount of torque you can apply to the wheels before slipping. If you want to control your slippage you have to control the torque, this can be done through a boost controller that limits boost on throttle position and rpm. The torque can be "curved" to only increase in the upper rpms where it can become usable.

I did, got the diff from an auto 350z so it's a 3.3 vlsd. I guess I don't have a lot of info though since I swapped before I went FI, and I haven't really launched my car yet (still getting used to the new power). It seems like everyone has traction issues in 2nd even from rolls though, and while it spins into 2nd if say I do a 20 roll from 1st and then shift into 2nd, if I'm going like 35 and mash it in second it kinda chirps and then grabs.

oooorr you can put a 3.33 rear gear in like he is suggesting and reduce the torque delivered to the wheels by 11%. FYI that is why nissan puts a 2.66 rear gear on the m56

most porsches and supercars with "more traction" also happen to be gear 10-20% higher than the factory z. the more torque you have in a light car, the higher you you want the gearing to be control delivered torque.

Yeah look at the ZR1, thing does like 66mph in first gear lol. Probably a big part of why it's 0-60 is so fast

Edited...

There are other consequences of the switch that have kept me from doing it thus far. First, SRM will not work well the farther you get away from the factory MT rear end ratio. My guess is 3.53 is not that big of a deal, but 3.3 could be. Also, cruise control will not work properly in at least 6th gear with even the 3.53 (I believe) and definitely not with the 3.3. I can't be without cruise control!

Yep, did lose cruise in 6th gear (which is like the most important one lol)

Just an FYI the factory MT rear end ratio that is in your car is already 3.69

Can a tuner adjust SRM to match a 3.3 gear?

You can with ecutek. I'm running the 350z 3.52 final drive and the SRM is close enough to still work well and you don't lose cruise control like the 3.3 does, but 3.3 is your best bet for a twin turbo if you want the most traction, no question.

exactly. another example are the twin turbo 1/3 series BMW's that have a 3.0 final drive as well and don't have anywhere near the traction issues we do while running smaller tires and better 1/4 mile times.

I did the 3.3 in my 350z and it was worth it. I plan to with my 370.

dang, I didnt know the 370z dropped cruise with the 3.3. Hmm, I will have to ponder why the cruise control cares about the final drive. I figured it would just be a wheel speed based thing, and it would adjust throttle to achieve the target wheel speed. Anyone clear on why we lose cruise? I am drawing a blank at the moment.

Anyone know if uprev can do it?

No idea... Didn't a vendor fix it when the auto guys went from 3.357 to 4.08? Could it be the same fix?


And using cruise control in 6th vs 5th shouldn't save THAT much gas if you're actually cruising. And the gears will be longer, soupy might be close to the same revs in 5th with the auto diff vs 6th with the MT diff

It can not

This may sound weak, but I am not so sure I can live without cruise control. I am alreaady living without window washer capabilities and that is hard. If I loose SRM, big WHOOP. If I loose Cruise Control, "Damn Son, where'd you find this?!?!?" Would make the drive from TX to MD kinda sucky!

But we still don't have the hard data only feelings and opinions, is here someone who measured it? I mean for 1/4 mile time before and after the final drive swap ? Or I have to do it as a first one ? :)

MrSqueeze is running 3.3, I dont think hes been down the 1/4 with it yet though and his car is currently down while switching to the BP kit

I really don't know why you only loose cruise in 6th, Squeeze did warn be about it but I figured oh well. I wonder if in my case it's cause the 350Z was a 5 speed auto and I have a 6 speed? Idk wild guess

D'oh. Sorry, there are two other ratios that I have heard of, but I couldn't remember what they were exactly.

Then maybe he will advise something...

I feel that the car will slow down in the 1/4 mile with the gear change.
Z

Some say very much different - more grip and lower 1/4 time...please remember we are talking about FI car.

More grip through reduction of power applied to the pavement. The car will loose some acceleration in each gear. With stock gearing, the placement of the 5th gear change is inconvenient and it's really difficult to consistently get a clean 0-60mph part of the run. So quicker 1/4 mile times from stretching the gear out is more of distance specific side effect... Making it really hard to say precisely how much quicker it might make your exact car with you driving it. Because given the right tire, alignment, suspension setup, and driver... The stock gearing is quicker.

Yup, Turbo you want to stay in boost as long as possible, 3.3 will help with that. S/C you will want to reach redline as fast as possible, so lower will help.

Wish I had a manual guy in Hawaii who wanted to Trade. I'd love a 3.69 on my 7at