4.08 Final drive - feedback please
 

I am considering buying the Z1motorsports final drive kit with install parts etc.

I have read a few threads on peoples experiences, but wanted to ask directly for FB based of personal experience and opinion.

Shoot :tup:

I was considering getting it, the only thing stopping me is that is throws off SRM a bit and can cause it to turn off under certain situations (jnaut says its not off by much and doesnt normally notice it though).

Aside from consuming slightly more gas mileage I can tell you the car pulls quite a bit more over the stock gearing. chuckd05 and I did a "comparison" and he pulled about 2 cars on me by 80. He seems to really enjoy it, from what I remember he lost maybe 2 mpg.

Hopefully some others can chime in, but if I didn't have SRM I would probably be running the 4.08's myself :tup:

Useful info Bro

newb question.. SRM?

Good info, I'm on the fence with this as well.

SRM - Synchro Rev Match

Yep - good info - need more user input

Dont mean to thread jack, but some things I would like to know.....

What does it take away on the top end? Like MPH differences.

Do I have to take it out when I get my SC?

What is RPM's at 80 MPH?

Thanks!

No thread jack that, all relevant to this thread, any one with ?S stick em in,, more info the better..

Id like to know estimated cost to get installed, I got the kit covered.

Top end you likely won't find out, jnaut has reportedly gone 167mph with his 4.08's so realistically it is not an issue.

You don't have to change out the gears when you get your SC, you just might have have more traction issues. This would be a bigger concern for people going with turbos because the torque comes on so strong they struggle for traction as it is, 4.08's would be tough. The SC is very linear power so I think it's controllable, just get some bigger/stickier rubber and you should have no problems.

Speaking about the manual transmission, from what I remember 80MPH in 6th gear is about 3200-3300 with 4.08's, +300rpm over the factory 3.69 gears.

A rough price for install provided you have all the parts would be about $400 labor. You may or may not need shims from nissan to get the proper tolerances during the install which your shop would let you know about, they don't cost very much though.

^My budget all in was about 1500 bucks so looks a go go, thx for information

Shouldn't need to spend more than $1200 with all the parts, do it! :driving:

I have 4.10 in my G and have NO complaints. Love it...

Thanks! +rep

One more question I forgot to post before are they ok to run in the 7AT?

If so this is enough info for me to pull the trigger soon as well.

4.10 does Z1 sell that in a kit as well?

iirc, the autos loose cruise control w/4.08's (but the manuals don't).

good info in this thread. I'm considering them at some point as well.

as jnaut pointed out in another thread, 7AT has a different carrier inside the diff so the gears dont bolt up the same, you would need to start with a manual differential and then I believe you lose cruise control. Also the final drive in the 7AT is 3.3, you might just want to grab a used manual diff with the stock 3.69 gears, and call it a day, 4.08 would be pretty aggressive for you.

Have you finished install on this update? :) I'm interested how you're liking it.

I have a thread about going in the opposite direction with the axle ratio.

Not even got parts as yet but thinking on it,,, 2 of my 4 kids at docs this week so just dropped 700 bucks, on hold for a little while, but will get it done.

I'm hoping to make this switch soon.

The 4.08 's work great with my 7 AT. 1/8 mile in 8.01 seconds, the 1/4 in 12.42 @114.3. Im turning 6000 rpm in 5th.
The diference in rpm is aprox, 700 to 800 rpm more and fuel consuption goes from 37.5 to 31.5 mpg.
2nd gear is the gear of punishment as the car just screams. Now hold the gas and brake at 2200 rpm and launch the car . It becomes a cruise missle. I shift at 7800 to 7900 rpm.
3rd gear is also very powerful and fast.

Is that really in the 30s for you?? :O

whaaa 37 mpg?

I found that the 4.08 gears are too much gear for the manual transmission drivers. The shifts between 1'st and 2'nd are so quick, I bounced off the rev limiter far too many times in first and second gears. :eek:

The SRM seemed to be out a few hundred RPM but either it has adapted or I'm use to it now as I barely notice it.

I've changed my rear diff to the 3.9 gearset from the 4.08 and hopefully this will make the 1'st and 2'nd shifting easier, SRM and less rev limiter bounces. :driving:

Time will tell.

I have the 4.08s and have no complaints.. i took videos of myself at different cruising speeds before and after and i forget the exact difference it was but it was only like 4-500 rpms... at 80 i think I'm at 3500 or so... for some that may be too high but I still get 24+ on highway and 15-17 city... This really all depends on your right foot though, the FD def didn't hurt the gas substantially...

I myself don't have a problem hitting 2nd, its not all that quick IMO, top end wasn't hurt that much at all but the final drive does help you down low more than up top... the car "feels" much faster and its faster but not like night and day you know...

but note the two best times for us 370s have 4.08 FD, one auto (z elim ) 1 6M....

i went 12.94 without the final drive but have yet to go back... swapping to 305s and the GTS's helped with traction from my stock sized nt05s that were worn down when i installed the final drive... the worn tires had a little traction issue in first after final drive...


also note that i do not have SRM so i can not tell you how it effects it... my right foot works just the same as it did before the install tho!

Is it worth the money ? I am sure, its up to the person... If you plan to go FI at any point, obviously don't do it.. but if you want to optimize your car NA'ed than go for it..

Ok , you will lose cruise control with and auto on these gears, top speed not so much as i have gone 167 with limiter removed. i usually charge about 1100$ for the gears installed so this will help you to have an idea on cost. The SRM will be off about 300ish rpm. I have had the SRM shut down from time to time doing high speed runs , typically 120+ speed. I have not installed the gears on an auto yet, but i do know the carrier is different from the auto to manual. So i can to be sure the these gears will bolt to an auto carrier. to be sure you will need to find a manual diff from a 370 or later model 350. I have heard that the diff from the 350s will fit but the pinion flange is different, so that will have to be swapped, no big deal. The gears will make a HUGE difference !!
Also if you need the gears let me know as i can get them at a great price!!

^ pm price?

ok i will tomorrow :)

Jnaut, I have a quick ? regarding the 4:08s.

Our car will be seeing it's share of HPDE track days. Obviously the gears are a big improvement for drag racing, what would be the pros and cons for track use? I've gotten conflicting opinions on the gears for track use. Thanks.

I think he meant 27/21. Z since you seem to be the only 7AT to chime in on this I would benefit asking you some more direct questions.

How has your SRM been effected?
What is your RPM's at 80 considering this is my average speed in the interstate.

Thanks!

J would you be willing to source all the parts I need to get this done on my 7AT?

Thanks everyone has been given rep that has helped me!

My gas milage is in Canadian gals. Converted to US gal it would be 31.25 and it droped to 26.25 mpg.

Z

Jnaut - full install kit price PM please...

What about your RPMS at Highway speeds?

Is there any way to keep the cruise control on a AT? What if the swap out was just for the manual gears?

I have a g37 7at with 4.08's and my cruise control stays usually but sometimes it doesn't work (no idea). My 1st gear is 30mph, 2nd 45 mph and 3rd 60. I have to be at 3rd to get to 60 and was wondering if a 3.69 / 3.9 would be better suited and what each gear will take me to?

Not to get too far off subject. Can us 7A/T guys swap over to manual and have it bolt up or what would we need?

Thanks

I've been driving with the 3.9 gearset for a few miles now and found the difference between the 3.9 and 4.08 driveability much better. The SRM performs flawlessly and no real differences in rev matching. The acceleration is more linear with no bouncing off the rev limiter anymore.
I've noticed that normal street driving is now more in 4'th gear; 80 Km/h @ 3000 RPM; 60 km/h @ 2500 RPM; instead of using 5'th gear for street cruising. 120 km/h is 3000 RPM in 6'th gear and instant passing acceleration, when you need it. I am much more content with the 3.9 gearset, versus the 4.08's.

Just my 2 cents

4.363!

Interesting, I didn't know there was a 3.9 option from nissan, I only saw an aftermarket gear that looked quite expensive. This might be on my list when I finally upgrade my LSD.

I love my 4.08s, they add great low end and liven the car up ....

I have absolutely no complaints with anything

^^ how about top end? Do 4.08 gears kill top end acceleration? like in the freeway

nope not at all, your rpm will be higher so it will act will help on freeway acceleration unless u cruise doing 150 lol