it's just a recommendation due to traction issues. with 4.08's and boost you will have a harder time keeping the rear end in a straight line and you will run out of gear quickly with all the extra power.

I've driven an all motor Z with 4.08's. you don't want to run boost with those gears.

so at normal speeds what are your rpm's and does this effect the temps any on regular driving or is your car oil cooled?. im from texas so i dont know if the shitty weather has something to do with it, but if ur at a high rpm for a "long" time the temps can start to change quite a bit.

Great thread man, thanks for all the info ...

I'm doing this in my G - where's the place to order these?

Yes I do 4.08 and 500 rwhp with drag radial at 15 lbs = 11.3? 1/4 mile times
and a fully glued lane. Shifting at 7800 rpm/ God bless the 7 AT.

So what's an estimated total cost to do this for a 7AT?

if you already have traction problems with 300+ rwhp what makes you think it will stick with 500rwhp?

Just a heads up to those with SRM wanting to do the gears: If you have an upgraded clutch, the 300rpm difference is EXTREMELY noticeable both on up and down shift. In order to get smooth shifts you need to slip the clutch slightly as opposed to just letting off immediately like you could normally, otherwise it makes for an unpleasant ride.

@tranceformer and jnaut -

In the parts list you guys don't list the side carrier bearings/seals - and you list the front shaft seal as optional? Can you get that off and still reuse it? I notice in the FSM it says not to.

Do those side seals/bearings need to be replaced as well? I notice all the retail "install kits" include those. Wondering if maybe with 25,000 miles on my G if I should expect to replace those as well?

Just get the gears from Z1 and order the install kit with it. Comes with everything needed.

With air preasure set at 15 lbs on the 305 35 18 drag radials and a good burnout with the line lock. They should hook good and stick to the track.

Actually it doesn't - you have to order both kits from them and pay way too much for them.

I got everything needed for $660 shipped. Buy from them and you'll pay $900+ with shipping.

from Nissan?

And just to be sure no welding needed right? I remember reading something about welding when I was looking for prices online.

No welding needed. And parts for mime from Nissan were $980.

PM me I can get all parts needed and ship them to you at a discount.

Now he chimes in! :bowrofl:

Thanks for the offer though!

I just placed a second order- decided to replace the seals / bearings all the way around. New total for everything is $810 shipped - still a couple hundred cheaper than Z1 and others though. I used nissanpartsdirect.com and Infinitipartsonline.com.

Sorry my fellow z owners :(

Don't worry about it man, better late than never! :tup: :tiphat:

So to confirm, the parts list is the same for the 3.9 final drive swap with the exception of the ring/pinion which appears to be part #: 38100-0B66A?

Wanna make sure I can use that part number for the final drive, quite a bit cheaper than the Tomei 3.9 set on Z1Motorsports.

3.916 Frontier gears
 

I'm currently running the 3.916 Frontier gears (38100-0B66A), w/no problems. I recommend a clutch LSD while you have the rear diff opened up though- that was the most noticeable difference. If and when open source reflashing :confused: becomes available (a La ECU Flash for EVO) for the Z34, I'll definitely upgrade to the 4.363 (38100-0C860) :eek: ring n pinion w/a good lean tune below 3,500 RPM.

Cool thanks for the info! I'm looking at the same LSD too, did you order yours off Z1Auto?

I got the gears put in on Monday and wow, what a difference it makes. I was apprehensive about it being too much and it affecting drivability - not at all. I read someone say it's like the car is on steroids now and thats the best way I can think to describe it. Pulls much harder - best mod I've done so far.

Just some info for those that were wondering - in my 6mt, 3000 rpm puts me at 73 mph. About 300 rpm higher than before, but not an issue at all. Doesn't have that "need to shift" feel at all.

Only downside is I do have some "gear whine" at about 40 mph when applying drive input to maintain that speed. If I let off the whine goes away during deceleration and coasting, the shop is going to adjust the pinion pre load and should take care of it.

Will update with the adjustment. Best $1100 I've spent on the car by far!

^ do you feel that your top end it must "farther" or limited now that you have the gears?

top end is not hurt at all by the gears unless you're crazy, you CAN hit 160mph+ and you will get there quicker with 4.08's

agreed - I'm still technically "breaking them in" but I have access to a runway where I'll soon test 'em out. But practically speaking, no, no noticeable difference. The car just feels like it needs to keep going .... so fun to drive now.

On the downside, and I'm hoping maybe jnaut and tranceformer will chime in, I talked to the shop that put em in today. Told him about the whine under light acceleration, just enough drive input to maintain speed, and he acted like there was nothing more he could do - he said the mesh pattern was perfect, and then gave me the dreaded "some gear sets just whine ... can't tune em out"

Told me to drive it for awhile and let everything "seat" and see if it changes any. I'm also going to switch to Redline 75W90 to see if it helps any. But I don't think it will. Any reason to believe that this may work itself out after break in ???? That just doesn't make sense to me ....

So I'm hoping you guys can give me some ammo to go back with ... as far as specific adjustments. Anyone else see this? Any experience with pinion preload adjustments? Mesh patterns that work better than others i.e. more toe, or more heel patterns? Anything that will convince him to break into it again and make an adjustment.

Aggie you have a pm

Anyone do this to the 7AT yet? I really havent seen anyting about it with the auto tranny...



DAN

Im considering shipping my diff and gears to a specialist - since i have been unable to find someone good around philadelphia. any suggestions around the east coast?

I'm interested in doing this on my 7AT too. Information on that would be helpful.

THanks

7AT
4.924
3.194
2.043
1.412
1.000
0.862
0.771
3.357 (Final Drive)

6MT
3.794
2.324
1.624
1.271
1.000
0.794
3.692 (Final Drive)

Multiply gears by FD.

7AT
16.530
10.722
6.859
4.740
3.357
2.894
2.588

6MT
14.007
8.580
5.996
4.693
3.692
2.931

6MT (w/ 4.083 FD)
15.491
9.562
6.631
5.189
4.083
3.241

Now look at 7AT vs 6MT w/4.083:
7AT 6MT
16.530 15.491
10.722 9.562
6.859 6.631
4.740 5.189
3.357 4.083
2.894 3.241
2.588

The first 3 gears in a 7AT w/ OEM FD is geared more aggressively than a 6MT even with a 4.083 gear. The top 3 gears favor the 6MT, even without a final drive, the gears are closer. Up to 3rd gear the numerical values favor the 7AT, but the 6MT spans the 4-6 in what the 7AT spans with just 4-5.

I realize I am a little late on this...but regardless.
 

:tiphat:

I will look into our pricing. I attempt to keep our prices as competitive as possible. Thanks for the heads up though. I know it may not benefit you directly, but any comments about this and future price concerns. Please feel free to shoot me a PM, I am always willing to double check prices on our website (bc they do change from time to time) and will work to the best to my ability to price match whenever possible.

Z_eliminator has it done on a 7AT :tup:

so for those with the M/T does the sychro rev match still work the same?

if you bothered to read or search the thread you would know that SRM is off by a few hundred RPM as the system is pre-calculated with the factory final drive. With the stock clutch its not very noticeable at all and you wont have any problems*, with a stiffer aftermarket clutch you will likely be so annoyed that you disable it.

*the one issue is going over ~130MPH will cause SRM warning's to appear and the system will disable itself until you turn off the car.

well, I didn't bother to search through the forum... thank you for the answer however.

Actually it was in the earlier part of this thread....

I had just seen on a forum before that it affected the SRM, so I didn't even bother to consider it as a mod.

not with a lot as I read before. it's is the most noticeable mod for an NA though

Little OT here BAQ but how is your experience coupling the Quaife with the 4.08's?

4.08 gears for AT
 

Has anyone does this on an AT, and where can you find them?