4.08 Gear Install (7AT) Review

reldas

can i just get a manual differential and install that in a auto, without getting the 4.08 gears? is there anything else i would need? like a Stub Shaft assembly. sorry for the questions still learning.

dthem370

As far as I know they should just bolt right up. I don't think any modifications or additional parts are needed if your just swapping the entire differentials. I do believe that the cruise control will no longer work still. People on the 350Z forums were switching to different size gears and also the manual diffs and they were losing their cruise control as well.

jvg

What exactly is the difference between the auto and manual carriers/diff? Just curious as to why you have to swap to the manual carrier/diff to do a gear swap.

dthem370

I'll quote Jnaut on his explanation of this from his thread,

"the diff housing are the same between, the difference is inside , the carrier ( where the ring gear bolts up). you would need to change that carrier plus the stub shaft and axle if your going to run lsd or get a manual rear end out of a 350,g35,g37,370z."

NickD

I don't understand why the 7AT loses cruise control from doing gears. My biggest concern with that is UpRev uses the cruise control button to set the maps so will doing gears on a 7AT screw up UpRev?

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Z eliminator

up rev works perectly for changing maps with the 4.08s

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12.343 @114.14 . 4.5 stroker motor is now being built. Dec 1 2015.

wstar

Thanks for reporting on all of this.

Yeah I don't think the cruise control loss would affect UpRev switching. It's more about RPMs + wheel speed sensors not matching up the way the ECU expects that kills Cruise Control.

Q's:

1) Does VDC work now or is it forced-off? (which might actually be a good thing!). If it still works, does it seem to work correctly or does it make even worse corrections than usual?

2) The "manual rear end" thing... was your car a Sport Pkg 7AT with the VLSD before, or not? I'm just curious if this was about your rear end not being a factory VLSD, or if it was actually about the manual/auto thing, because the service manual doesn't seem to think there's much difference between manual/auto at the back, just VLSD -vs- Open.

3) You said 7AT revmatch "seems" to still work, but you needed to do some "sport mode" driving... that makes me a little leery yet since we don't know we're on the same page here. Can you drive the thing around in Manual mode and actually downshift, e.g. 4 -> 3 or 3 -> 2, and the rev match happens correctly for a smooth downshift (try it under braking, around 3.5K RPM in the higher gear before the shift).

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kcquinn49

If your car had the power, I'm sure this statement means that with the 4.08 gears you are rev limited to 180 vs 200 mph. That is the way I read it.

Z eliminator

wWill let you know when put the stage 2 and stage 3 GTM Sc on it, i have the limiter set at 8200 rpm now all moter,

Z

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12.343 @114.14 . 4.5 stroker motor is now being built. Dec 1 2015.

wstar

180 isn't an unreasonable speed goal given a few mods and whatnot. I know for a fact the factory car can hit ~155-160. Somewhere right around there the ECU speed limit kicks in (which UpRev can eliminate). I kinda forgot about all that after I had UpRev on the car, since I really don't have any reason to try to go faster than that, but I wouldn't be shocked if the drag limit was a bit higher. Has anyone actually tested a bone stock 370's drag limit on flat ground without significant winds?

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SPOHN

IMO around 180 and up is where aero dynamics play a hugh role.

Lets hit the salt flats baby.

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Z370Z011

Will the gears affect a 6MT cruise control as well?
This review sold me on the gears! Killer write up!

Dwnshift

FYI.... We are just above 170mph at Daytona... Sooooooo unless you are tackling the salt flats there isn't /shouldnt be a problem.
Easy swap go to : www.car-part.com search and purchase a rear carrier / housing from a manual Z from salvage yard. When going that route...there will probably be less of a chance at needing to shim the diff unit itself when swapping gears...giving you a better line up on the gears and less gear noise.
Plus when selling the car etc... Makes putting It back a breeze.
Hard searching you can usually get them for $500 shipped. (entire complete rear carrier) you will have to use a little elbow grease when it arrives as the outside of the casing may be a little site to the eyes...but it's what's inside that counts.
The viscous lsd's have one half shaft that is slightly longer that operates the viscous unit. When switching to a clutch type LSD... And I highly recommend OS Giken unit.... You will need to purchase a Left side half shaft from Nissan.( shorter of the two shafts)
Any guys seriously tracking the cars ...or not. I would seriously recommend sending the 4.08 gears to be micro polished.... It can cut down rear end temps by about 15-20 degrees... Doesn't sound like a lot....but it is with how hot these puppies run.

wstar

Personally I think 4.08 might push me off into 5th gear too often at the end of short straights in the 7AT, but I was considering upping to the manual's 3.692 ratio when I put in a clutch LSD, assuming it doesn't end up screwing up the 7AT's smooth downshifting. That's my main concern. You'd think it would just operate on RPMs, but the reports of 6MT's SRM getting screwed up makes me question that on the 7AT.

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dthem370

1. VDC still works perfectly fine. It does come on more than before because of course there is less traction now with the 4.08s.

2. My car was a sport package 7AT before and I swapped to a sport package manual differential. So basically I had the stock VLSD before and after the swap.

3. Yes you can drive around in manual mode and shift up or down. To me it feels perfectly fine and I do drive around using the paddles and shifter often. I have tried it under braking and it feels the same as how it was when stock. The one thing you will notice is that you will need to shift much quicker out of 1st and 2nd gear because of the gear swap.

No it does not screw up Uprev. You can still switch between your tunes like normal.

From my research it seems like the manuals cruise control still seems to work fine after the gear swap.