LongFellow

Finally a TECH question...

The 350z has a Final Drive of 3.54 vs. the 4.083 of the standard open on a S14. Would swaping 3.54 into a S14 give it a longer gear ratio equaling in less acceleration and gaining higher top speed?

Reason I ask is im in the process of swaping a Z33 6spd onto my KA and was wondering if I should look into getting the Z33 Differential along with it. Or just see how it works with the factory S chassis unit.

dan

if you're just swapping the transmission, i would do the calculations first to see what kind of numbers you're going to get with just the tranny alone. 6 speeds usually are geared alot differently than 5 speeds, so changing out the final drive/diff isn't always necessary.

i cant give you an answer. just putting the 3.54 diff in would definitely kill acceleration, and like epstein mentioned in the other thread, the higher gear wont necessarily help since you could achieve similar results with more power and tire sizing.

if you go through with it, let us know about how hard the transmission is to get in there. i know the shifter is longer and you'll probably have to modify the fork assembly coming out of the back for the shifter to fit in the stock hole (depends, since the only times ive seen it modified is when someone put in a vq or vg engine so it might not need any changing?).

i wouldnt mind having a 6th gear for highway driving, as long as the other factors of acceleration dont change too much.

EludeR

Their was a post on freshalloy about a guy that swapped a maxima VQ30DE mated to a Z33 6spd, I thought it was pretty clever. He modified it so that the shifter fit in the stock location too I believe, i'll digg for the post and repost with the link if I could find it.

Epstein

3.54 is a good ratio for the 6-speed, but I'd look at the 3.7 also. I've got a 6-speed in the garage waiting. I'll probably be going with the 3.93 with my medium torque SR and 8k rev limit.

By the way, one 6-speed swapping trick is to buy a Frontier 6-speed rear housing. It bolts on and has the shifter built in coming out of the top of the case, instead of the back.

LongFellow

I did the math ratios and here is how went (calculations are with FD multiplied in)


KA / FD of 4.093
1- 13.559
2- 7.765
3- 5.340
4- 4.083
5- 3.098

Z33 / FD of 3.54
1- 13.416
2- 8.227
3- 5.735
4- 4.496
5- 3.540
6- 2.796

Trans swap
Z33 / FD 4.083
1- 15.474
2- 9.488
3- 6.614
4- 5.185
5- 4.083
6- 3.226

LMK if you find any errors in my thinking. Gear ratios is new for me.

It seems its going to Accel faster and possibly use a bit more gas in top gear even with a 6th. So I think after having a little fun with the more acceleration I'll have, Im going to swap out the FD for something a bit longer.

Doesn't the J30 diff have a longer FD? what car has a 3.7 FD?

I'll make a post about the project when I start it sometime later this month.

LongFellow

I already have the transmission sitting in the garage now, so Im going to measure how long it is on both transmissions from the bellhousing flange to the center of the shiftlever then make a shift fork bracket like they do when swapping the whole VQ drive train, They said it has to move forward 4 in. with the swap so Im hoping mine is close to the same because thats about the maximum I can move it forward.( i might be able to make 5in)
If that dosnt work, Ill look into what Epstein said about the frontier rear housing.

Custom drive shaft isnt hard to get made, and I have the
Z33 crossmember which i will just modify.

and Im looking for a Blown KA block and crank I can pick up from some one so I can figure out how to mate them together. Im hoping I can just re-drill some new holes in the back of the Block side and thread them. I really dont want to have to make an adapter plate. then then cut a section out of the Z33 for the starter to fit then make and weld on a sheet aluminum cover. Or thats the plan for now. (always gotta have a plan..lol)

Epstein

Ahh now we're looking at the overal ratios. The highlights here are the first gear overal an the ratio between first and second (usally the biggest ratio).

You can see that with the Z33 + 4.083 you get a pretty big first gear multiplier. You're not going to put 350ft-lbs down through that without slicks. It would be pretty slick on a small turbo KA, but I doubt budget people are looking to do tranny swaps. The Z33 + 3.69 will give you right at 14.0 in first, which would be nice. The 3.69 came in later Q45's (97-01?), and Nissan Motorsports offers a 3.7 kit for the 350Z, but it's $$$.

The other point is the 1st to 2nd ratio. Take smaller number over bigger number, which will give you a number smaller than 1. Multiply by your redline (or 1st gear shift point) and this is the RPM you'll wind up with in 2nd after the shift. The Z33 gear keep the RPMs up into 2nd. This is what they mean by "close ratio", although this is just "closer". With a 7k rev limit and KA trans, you'll be at 4000rpms in 2nd after the shift. This is below the full boost threshold for a lot of 450+whp KA's. The Z33 trans will leave you at 4300rpms, which is better. These calcs are independant of final drive, by the way. Doing the division by straight gear ratios or overall (fd included) ratios will yeild the same number.

The J30 has a 3.93 FD and is bolt in.

LongFellow

Thanks for all the information.
I see what your saying but my car isnt going to put down any huge numbers anytime soon.

Im looking into a mild KA-T build by next summer. Something around 250-280ish hp range. I figure with this transmission and a J30 FD it should be a fun car to drive.

Im going to try to keep this swap under 850$

Epstein

This is exactly what I'd do. Good choice!

norachelhere

good info...
i'm glad to see the nissan world is getting more creative with their builds...