Help G37/370Z 7AT FAQ Mega-Thread! - MyG37

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Help G37/370Z 7AT FAQ Mega-Thread!

Old 08-18-2017, 01:30 AM
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Slatey
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G37/370Z 7AT FAQ Mega-Thread!

I'm putting together a FAQ for the 7AT because it is quite the topic of discussion for our cars and the 370Z. Regardless of your opinion of automatic transmissions, this thread is based solely on facts and questions surrounding the 7AT. I have pulled a lot of information from many sticky's, threads, and other forums into this one thread.

Q: My car seems to jerk while decelerating and at low speeds, and I have rev flare between upshifts like the transmission is slipping. Is this normal?

A: Yes this is normal, especially on early models. The 7AT on the G37/370Z (Nissan/infiniti JATCO JR710E) have a special torque converter that can cause odd behavior that don't happen the same way they would on a normal automatic transmission. Here is a quote by Nissan NA

Originally Posted by Nissan North America
All modern automatics have a lockup torque converter, which limits slippage by creating a solid mechanical connection between the engine and transmission. For smoother operation over a wider range of operating conditions, newer designs vary the amount of converter lockup (from a 100% solid connection to a partial lockup condition).

Infiniti’s 5- and 7-speed transmissions use a multiple disc torque converter lockup design that allows the unit to “ease” into lockup, minimizing the shudder that can occur in single-disc designs.

While Infiniti is not the first manufacturer to vary the level of torque converter lockup, it has created an extremely wide available lock-up range with the new 7-speed transmission:

With the transmission in Drive, partial lockup is available in 2nd through 7th gears while full lockup occurs in 7th.
With the transmission in manual shift mode, both partial and full lockup are available in 2nd through 7th gears.
Some amount of lockup occurs at all throttle positions and at speeds greater than about 15 mph. The result? Infiniti's 7-speed transmission provides a more direct, solid-feeling connection than drivers typically expect from an automatic transmission.


Q: That sucks. How do I stop the harshness and rev flare?

A: The simple way that seems to remedy a lot of issues people experience is to have the dealership update the ECU/TCM with the latest TSB, ITB12-027d. Most have noticed marked improvements in harshness and reduced rev flare, while others also report that it tamed the transmission to be far less aggressive (lazier shifting).

Q: Will an aftermarket tune improve shifting?

A: In most cases, yes. Both EcuTek and Uprev can increase line pressure for the transmission, making shifts quicker and firmer. They can also tell the transmission when to shift in the rev range based on throttle position.

Q: I have an aftermarket tune, can I still get the TSB?

A: Yes, you can still get the TSB. BUT since they also flash the ECU along with the TCM, it will overwrite your current tune and change the ECU information, making it not possible to reflash your tune without getting a new tuning license from your tuner. For more information about how that would work, speak to your tuner. The easiest solution would be to get the TSB first, then the tune.

Q: What ways can I improve the 7AT?

A: There are a few ways (depending on how deep your pockets are) to improve the 7AT. Some are these solutions are helpful to those going forced induction (I'll discuss this later).
Listed below:

-A grounding kit is one way people have noticed drastic improvements to the 7AT. The theory behind it, is that improving the ground between key points in the engine bay improves signal to many components of the drivetrain and electronics in the vehicle. DIY and discussion is in this thread. In my opinion, I feel like this restores transmission performance lost over the miles and years, not necessarily improve it.

Note: Some have stated that there is a battery current sensor and bypassing that may throw off charging rates or cause battery issues.

EDIT: After performing this grounding kit, I started experiencing issues with knock. I went into it further here.


-An aftermarket tune can greatly improve the behavior and performance of your transmission.

-LEVEL 10 Transmission upgrade. Level 10 is located in Hamburg, NJ and for a pretty penny they will rebuild your transmission with upgraded torque converter and valve body. This will improve the 7AT to far more modern standards, giving it very fast shifts.

-GTM Stage 4 Upgrade. Similar to the LEVEL 10 upgrade. Video below.

Q: Nissan states the transmission doesn't need servicing, is this true?

A:
Short answer.
Maybe? Plenty of people have never serviced the 7AT and they are fine

Long answer.
While Nissan states that the transmission needs no servicing, many of user will disagree and would like to have the transmission fluid replaced. It is my personal opinion that it should be replaced, or at least checked, every 100k. Others recommend 70-75k, some even state as low as every 30k for aggressive maintenance schedule. Methods will be talked about next.

Edit: In a bulletin released by Nissan/Infiniti, the ATF Matic S fluid used in the 7AT does darken quickly, but this is not representative of how the fluid is actually wearing and lasts far past the point of darkening, according to them.

Q: I want to have my transmission fluid replaced, how do I get this done?

A: There are two methods to replacing the 7AT's fluid. Fluid change and fluid flush. Both processes are very specific to the 7AT (though similar to other transmissions. The 7AT uses Nissam Matic S fluid. There are other compatible fluids, but I would not recommend deviating from Matic S.

The fluid change is the safest and preferred way. The DIY and explaition of the process can be found here.

The flush is the most aggressive, most thorough way to do this. It is recommended you take your car to a Nissan/Infiniti Dealership to perform this process because it requires a machine and a couple "special" pieces of hardware.

Q: I'm going forced induction, how much abuse can this transmission take?

A: Though there is some debate, it seems like things start to break (or at least have drastically reduced life) around 400tq. I'd recommend getting the LEVEL 10 or GTM upgraded transmission if you are going for big power. LEVEL 10 states that the 7AT is particularly weak, specifically in the 3 highest gears and it is recommended that you get their "Bulletproof" package for additional toughness.

If anyone has more information, I will be adding more things as I get more information on the topic.

Last edited by Slatey; 09-02-2017 at 06:10 PM.
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Old 08-18-2017, 01:36 AM
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Is there any danger in upping the line pressure? Thinking about doing all these things.
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Old 08-18-2017, 01:45 AM
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Originally Posted by future62 View Post
Is there any danger in upping the line pressure? Thinking about doing all these things.
Seems like a pretty standard thing to do for tunes from what I've seen. I'm sure there is very slight danger. Since the some engineer somewhere decided on the line pressure and designed with that in mind, but IMO the hardware involved can probably take the increased pressure just fine.
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Old 08-18-2017, 01:53 AM
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During my conversation with Level 10, they claimed the 7AT was weak, particularly the top three gears.

I hope to have them rebuild my valve body. Part and parcel of this is an UpRev tune which they can do. Fingers crossed it'll happen this fall.
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Old 08-18-2017, 01:59 AM
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Originally Posted by slartibartfast View Post
During my conversation with Level 10, they claimed the 7AT was weak, particularly the top three gears.

I hope to have them rebuild my valve body. Part and parcel of this is an UpRev tune which they can do. Fingers crossed it'll happen this fall.
Hmmmm. Good to know! I hope to have info like this start showing up in here.
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Old 08-18-2017, 10:33 AM
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Good write up and references for sure!


Adding to the conversation, the 7AT is fairly weak and will fail eventually with added power. Level 10 offers their "bulletproof" service that does the TC, VB, and clutch packs. I have this and it has been holding perfectly at around 600-650awhp and multiple track days and hard launches.


When getting the transmission worked on and tuned for line pressure be sure to double check the components and if they need to be reflashed as a whole to ensure that the ECU and TCM communicate properly. This caused me a headache burning through clutch packs in the transmission a handful of times.
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Old 08-18-2017, 03:39 PM
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I guess I should see if I have the latest TCU update. Sure don't want the dealer flashing over the UpRev changes.
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Old 08-18-2017, 06:24 PM
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Nice write up. I might look into grounding kit.
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Old 08-18-2017, 07:24 PM
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Great thing is it looks like used transmissions are dirt cheap on Ebay. $400-500. So you could buy a used one, have it rebuilt, and get it put in with minimal downtime. Definitely something I'm thinking about for next year.
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Old 08-19-2017, 07:05 PM
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Sticky for effort ?
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Old 08-19-2017, 08:02 PM
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Originally Posted by Slatey View Post
Sticky for effort ?
Definitely!
And worthy of plenty pushes of the "thanks" button! Well done, although I'd go 70k miles for ATF service.
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Old 08-19-2017, 10:24 PM
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Originally Posted by blnewt View Post
Definitely!
And worthy of plenty pushes of the "thanks" button! Well done, although I'd go 70k miles for ATF service.
Thanks!

I saw lots of discussion of at what mileage the service should be done, so I just gave my opinion since no one really knows lol.
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Old 08-19-2017, 10:30 PM
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Originally Posted by blnewt View Post
Definitely!
And worthy of plenty pushes of the "thanks" button! Well done, although I'd go 70k miles for ATF service.
Updated for more info.
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Old 08-28-2017, 04:35 AM
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For reference, I just performed the grounding kit.

I already have a tune, but I noticed some change. Downshifts on 3rd and 4th are lightning fast, but they were quick before. So there is minimal change there. Upshifting during medium throttle are a little smoother now. There is less lurching.

All in all, I think it's worth the $20 in supplies.
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Old 08-28-2017, 06:34 AM
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Do you recommend a kit or piecing together the wires on your own? Also my G has like 45K miles.... is it too early to worry about a flush? I wanna get the low hanging fruit first.
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