7AT 3.692 Gear Review
 

Not much to say here other than it's awesome. Have a 3.692 final drive gear and a Quaife differential and it accelerates so nicely. Car is always in the power band it seems and is much more pleasant to drive around. Fuel consumption is not really affected. I averaged 24 ish on a road trip with some pretty fast driving. In 7th gear I'm at around 3k RPM's at 80mph. Only negative is that cruise control does not work now. Actually it works intermittently.

The 3.692 final drive gear with the auto transmission is comparable to a manual with the 4.08 final drive gear. Actually I'm geared shorter, minus 5th gear. Speedo is not affected.

Here's where my gears max out (MPH at 7500 RMP)

1. 34
2. 52
3. 82
4. 118
5. 167
6. 194
7. 217

If a 7AT owner wants a nice upgrade, find a manual pumpkin from a 350 or 370 and plop it in there.

Is that all you have to do is swap the pumpkin???

yeah

Is there any certain year or make for the 350Z pumpkin? I think that will be easier to find.

Thanks for the review :tup:

I heard EcuTek Tune can get your Cruise Control back with this Mod.

Sounds like a good Mod... What kind of cost?

What year/model pumpkin did you use on yours?

i'd shoot for a one with a viscus LSD at least, unless you want to get a Quaife too then it doesn't matter.

yeah i heard that too. need to save up for a tune! for a Quaife and gears it'd be 1200 + i think. mine is from a 2009 370z manual transmission

Are you sure those are your max mph's? I think mine are higher on stock rear diff? I can remember shifting out of third at just over 90 and in 4th at 120+

they should be higher on the stock 3.357 final drive gear. that's what's nice about the new gear, shorter gearing and much better acceleration. what's sacrificed is top end speed, but that's not really relevant here

good review only thing i would add is if it is a 350z pumpkin your are going to want to grab some 370z stub axles of the same type as the ones you take out becauuse the abs rings on the 350z have a different number of teeth

If your 7AT is a non-sport model will the swap with LSD still work?

:tiphat:

i'm going to say yes :) you're swapping out the 'non-sport part' so to speak. the only issue is cross platform with G37's. that doesn't work.

That's a lot of numbers right of the decimal point.

Thanks for the idea and making me spend more money! That should keep the supercharger screaming.

Hey Critical....
Any updates on your cruise control or drivability changes? Still wanting to do this Mod but waiting for a "sport" 370z pumpkin to pop up for sale used.

Thanks


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I installed a 350 pumpkin & did notice the teeth difference
 

Installed it anyway, and went drag racing the next day.

I don't have abs light on, but I also never needed to use abs. Would you think that I no longer have the abs working?????

Its hard to say all i can tell you is it thinks the front wheels are turning faster than the rear wheels by 2 teeth per rev. Its hard to say exactly how the abs and tc are going to react.

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ABS works fine. Just slam on the brakes to see lol.

Cruise control doesn't work, but I think if I clear random O2 sensor codes (complexly unrelated) TC will work. Not bothered to figure out why or if this is the case since I never use it.

I think he is saying he just swapped a 350z pumpkin in without changing the stub shafts which is going to be 2 teeth off per rev since the 350z's had different stubs

Edit: or wait he owns a 350 so maybe he used a 370 rear in a 350 so it would be off the other way.

I put a 370's pumpkin into my 350 because it had 4:08 gears. No problem doing it & the mechanic (dealer) didn't mention anything.

I took my 350 pumpkin with 3:90 gears & installed it in my 370. During installation a different mechanic pointed out to me that those rings were spaced a bit different. Since my 370z pumpkin was out already, I gave permission to make the change and see what happens. Result, no abs light but no cruise control. Had no issues with 370 pumpkin into my 350z car. :confused:

A day later :) I drove 3 hours to a track(Atco) just to see/feel the results. Had the car for only 3/4 days, so everything else was completely untouched.

Even with traction problems(water on track) the car pulled like a MF & of course went through the gears really fast. After it (auto left in D) shifted into 2nd. the car was really moving. MPH as high as 107 almost 108. I think that's great pulling power for a stock Z w 1,500 miles. Test pipes + tune 110+ mph ???? Will test the abs after it snows a bit :)

the manual 350z has a 3.53 final drive, the 370 has a 3.69. small difference, but worth pointing out

Yes EcuTek can get your CC back

Let me know when your ready !



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Actually you are geared lower. Higher Ratio #'s = lower gears. Pinion gear gets smaller on numerically higher gear sets ;)

I'm glad I re-read this post, as I was looking into 3.9's for my auto as 4.08's would be too deep for me. After recalculating, there is only 4% difference between the 3.692 & the 3.9's. For the added cost I'm going to go with the 3.692's as they will already be in the low mileage diff I just bought Thanks for saving me a grip of cash :tup:

Does anyone have a clear understanding on how the cruise control works in the 370z? Where is it sensing it's reading from? Also is there any speedo/ Odo correction available/ needed?

Thanks again :tiphat:

That's 1/2 of the gain right there. 3.53 is only 5% increase while 3.692 is right at about 10% increase. Thanks for pointing that out::tup:

If I didn't have my 3:90 gear pumpkin laying around, I would have installed a stock 370z 3:69 gear pumpkin. My car shifted into 5th gear before the end of the 1/4 mile, so the 3:69 gears set up would be perfect/ideal & easy to find & install.

I will make my 3:90 work by tuning & raising the high H.P. point to 7,500 rpm & shifting points apx. 200 rpm. to 7,700 rpm with a redline at 7,800 rpm. It should do very well at the track. Test pipes, maybe better tires plus^^^^^that will put me into the 12.7's/12.8's with stock intakes & stock mufflers. Also it's real fine as a daily street car.

it messes with the cruise control logic. the specifics are on the forum somewhere and possibly in the service manual as well.

Anyone know other sources besides eBay for a used manual rear diff?

I have been looking for a couple of months on eBay with no luck :shakes head:

bug all the boosted Z owners

You can always call around to junk yards, both local & on the internet. I'll keep an eye out for you

Soo just to be on the clear quaife only delivers through one tire while the other rear tire is just dangling not puting power down?? Sorry this whole thing of diff and gears scrambles my head hahahahahaha. So you can get a basis my car is a DD, No track, Ocasional Drag. Also I plan on doing it on a 350Z Diff manual base model to my 370z. I plan on doing the 4.08 gears and just for the benifit of the doubt 4.08 gears are shorter or longer???? Since I plan on adding a big punch to this combo.

You are a cool cat :tup:

Would be cool if an individual with such knowledge could chime in please??? Need to know before I go ahead and pull the trigger, Thanks :tup:

4.08 gears are shorter. The higher the number (which is really a ratio, 4.08:1 in this case), the faster the crankshaft turns per every tire/wheel rotation. LSDs in general allow for the car to put power down to the ground on one side if the other has no traction by locking selectively.

Let me explain I know Mechanical differentials can be a bit confusing I'll try my best to explain.

Open Differentials (Non LSD) work by transfering power to the tire with the least resistance. (Ex: park with half your car on dirt and half on asphalt, do a burnout and the tire sitting on the dirt will spin, if you turn 180* around and have the opposite tire touching the dirt and try again you'll notice the tire that is touching the dirt will always be the one to spin)

a Quaife differential works the opposite. it delivers power evenly or to whatever tire has the most traction. so say you are drag racing it splits the power evenly amongst both tires until one starts to slip then it starts to deliver more power to the tire with traction. (Ie you park half your car on dirt and half on asphalt, it'll burn out with the tire on the asphalt, then if you turn around 180* and do it again it'll still burn out with the tire touching the asphalt)

to answer your Question, for Final drives, the bigger the number the shorter the gearing. so 3.692 is longer final drive than 4.083

-Juan

That was very informative guys I really APPRECIATE it one last question, I purchased a Dynotune Nitrous Kit so that means going with 4.08 gears, quaife and a 350Z diff would be a horrible idea with my kit?? Of course ill upgrade tires but I want to know if I can do this combo so rather than investing on the gears ill just install my nitrous kit on my 7At....

you're way better off with the gears and diff. if you had to pick.

Damn :/ not what I wanted to hear seeing as if that's the case I will have to sell the kit and I bearly have about a month from purchasing it from a member from here.

Power is useless if you can't put it down to the ground.

how big of a Nitrous shot is it? 25-50-75-100-150?

Still debating between 75 or 100 shot, leaning nore towards 100.

personally if it where me I would install, the 3.69's but i would also do a valve body upgrade on the transmission before installing a 100shot on it (personally i wouldn't do nitrous all together but that's just me haha). with the gearing i probably wouldn't use the Nitrous in the lower gears of the transmission, but it will feel awesome on the later gears when you switch it on.

-Juan