KNOWLEDGE: All about the 240Z / S30 Automatic Transmission 3N71A / 3N71B

The Nissan Automatic transmissions from the Datsun 240Z / Nissan S30 Z cars are probably not the most poplar topic. Despite the high volume of S30 Z’s sold globally, the automatic transmission option was always a niche variant with not many buyers going for it. Recently, however, I get more and more questions regarding Automatic transmissions. In October 2020, I released t he original 240Z transmission knowledge post, which mainly focussed on the manual transmissions, but also included some automatic transmission sections. Since then, I have collected loads of new information and documents, and I have therefore decided to split the automatic transmission topic into a separate post for easier readability and less confusion. Here you go:

Disclaimer
As with all my knowledge articles, I tried my very best to get all information from trustworthy and official sources. However, I cannot guarantee that all information is 100% correct. If you have any correction, input or additional information, I appreciate if you let me know. I’ll update this post whenever I find something to add or change. I am not a professional journalist, but I put countless unpaid hours of work and years of research into this post and spent quite a bit of money to source a lot of original factory documentation, so please ask, before you copy anything. Thank you.

1. Introduction / History / Development
Already during the development of the S30-range cars, (Fairlady Z / 240Z), the desicion was made to offer some of the models with an automatic transmission. According to Hitoshi Uemura’s (Head of the S30 design team) “240Z engineering development” book, the transmission tunnel was originally designed to provide space for the BorgWarner BW35 3-speed Automatic transmission – the only automatic transmission available at Nissan at that time.

Borg-Warner BW35 Transmission

The BW35 was also used by Nissan in the Datsun 2000 / 2300 (Cedric) in this period, and throughout the Nissan / Datsun automatic transmission documentation, you will find several comparisons, references to and mentions of the BW35 transmission.

But Nissan, at their Yoshiwara plant, started to develop their own transmission, the compact “NissanMatic” 3N71A 3-speed automatic transmission for rear wheel drive cars. It was developed specifically as an affordable, compact, lighter, more reliable and comfortable alternative to the then broadly used BW35 transmission. In the spare parts service bulletin “General Information GI68-006” (from Dec. 1968) you can see that the “Nissan full automatic transmission” was introduced as early as September 1968 in export markets, before the S30 was even shown to the public.

In this Datsun 2000 / 2300 Super Six operation manual, dated March 1970, you can see that the 3N71A is already mentioned specifically.

In January 1970, JATCO (Japanese Automatic Transmission Co.) was founded as a joint-venture between Nissan Motor Co., Toyo-kogyo (Mazda) and Ford Motor Co. in Fuji City (Shizuoka Prefecture), with the aim to produce automatic transmissions and parts thereof. They continued the operation at the same Nissan Yoshiwara plant (from Jan 1970 = JATCO) and officially started the production of their first transmission in August 1970 in the same location. My understanding ist that it was the same (maybe slightly refined) transmission that Nissan already produced previously at the Yoshiwara plant.
Aside from many other cars, the 3N71A was used as an option in the S30Z production cars, and the extra space designed for the BW transmission in the S30’s transmisison tunnel was never fully occupied. In this sketch from Hitoshi Uemura, taken from a “Drive” magazine interview, you can see how the dimensions on the car were originally designed to house a Nissan Y40 V8 engine and the tunnel to fit a BW35 transmission:

In the following photo, taken from the Nissan 1964-1973 Chronicles book ypi cam see the JATCO Yoshiwara plant, with a 3N71B Transmission below, along some JATCO company data.

JATCO still is active today as one of worlds largest automatic transmission and CVT manufacturers and you pass by their plant when you take the Shinkansen from Osaka / Kyoto to Tokyo:

In this video, at around 9:47, you can get a glimpse inside the JATCO plant and how their automatic transmissions got manufactured and assembled in a quite automated assembly line (albeit i’m not sure what transmission models are visible in the video)

Over the years, the 3N71 transmission – in varous assembly variants – was used in many Datsun / Nissan, Mazda, Ford and other vehicles and got several updates, modifications, and later got additional gears and evolution names and installed in various cars until the 90ies.
I had the privilege to enjoy a ride in an US-Market HLS30AUV (HLS30-60213, 1971, 3-speed automatic) recently at the S30.world opening, and I have to admit that the automatic transmission is really smooth to ride with a nice acceleration and comfortable feel.

The Australian “Road and Track” Magazine review of the 240Z Automtatic car comes to a similar conclusion:

2. Function
The 3N71A / B is an fully automatic transmission, which works using a three-piece torque converter unit and two sets of planetary gears. The function of the planetary gears is set via two multi-plate clutches, a multi-disk brake, a braking-band and a one-way locking clutch.
Via the two planetary gear sets, three forward gears and one reverse gear are available. The change of the gear ratio is done fully automated and in relation to the driving speed and engine torque. The driving speed and the negative pressure at the intake manifold are continuously transferred to the trasmission, so that the best gear for best efficiency and power is always chosen at any throttle position.

The available gears / settings are
P – Park
R – Reverse
N – Neutral
D – Drive
2 – Manual 2nd gear
1 – Manual 1st gear
Here is the function description from the Japanese Nissan Automatic Transmission introduction brochure:

In the 3N71B Service manual, you can find the shift diagram of the transmission, which shows the kickdown area and the propeller shaft speed (rpm) in relation to the intake manifold negative pressure (= throttle body position).

In various Nissan documentation, you can find the acceleration charts for all the models.
In this example: On the left side the HS30A and HS30SA (dotted line) automatic transmission models, and on the right side the HS30 and HS30S (dotted line) manual 5-speed transmission models for comparison.

While JATCO also produced automatic transmissions for Nissan with steering wheel gear selector (as often seen in American cars) and other variants, the 3N71A / 3N71B in the S30 cars always came with a console / floor type gear selecter (“shifter”), as nicely visible in the following drawing:

A good overview of the basic build-up of the transmission can be found in the 3N71A service manual for the 240Z:

Here is a scan from the Japanese market S30 Fairlady Z operation manual, from May 1972, which explains how to drive with the Automatic transmission:

3. Market introduction:
While the first Z-Cars were sold to the public in late 1969 in Japan, and shortly thereafter in the USA, the previously mentioned start-date of the JATCO operation, and the need to modify the existing 3N71A internals for the S30 requirements, explains why automatic transmissions were only available to the S30 range of cars at a later point.

3.1 Market introduction Japan
The domestic market was the first to get the new automatic transmission, but only in certain models. the S30A (aka Z-L) was the “Luxury” variant of the L20 engine equipped base model
The implementation started with S30-02611: S30A in October 1970 (3N71A transmission)

In March 1971, the automatic transmission was also made available to the standard (non luxury) base model S30SA.
The introduction started with S30-04551 in March 1971 (3N71A transmission)

In October 1971, the HS30 models got introducted: A L24-engine equipped version similar to the export market Datsun 240Z’s. The HS30A (Luxury), HS30SA (base), and HS30HA (with G-Nose front end) were available straight from the beginning with the Automatic transmission.
The introduction started with HS30-10001: in October 1971 (Already with the new 3N71B transmission)

The information for the Japanese market can best be found in Various service bulletin books of the automatic transmission models, like this example:

Unlike the export markets, Japan had more Fairlady Z model variants in their range than only the 2,4L engine version (HS30), and most of them got the Automatic transmission as an option. The only exception were the PZ (Z432) or the PZR (Z432-R) variants with the S20 engine. This is best visible in the Japanese parts manual where you can find a nice overview of the production base-models with their different internal naming codes and which variant came with an Automatic transmission. Those who have an additional “A” at the end of the designation codes, were models equipped with an Automatic transmission.

To Introduce the suspicious “new” automatic transmission to the reserved public audience, Nissan released a large 8-page “Nissan Full Automatic” brochure in 1971, which explained how the automatic transmissoin works, what is the advantage of it, how the kick-down works, why this AT is better then first generation automatic transmissions from the past, what the fuel consumption rate is, if it requires increased maintenance, and if the existing Nissan dealerships know how to maintain such a transmission.
The brochure featured thoughts and inputs by racing driver and the 1970 All-Japan-Championship series winner Kunimitsu Takahashi, his wife Renas, and Dr, Kenji Higuchi (PhD Iin Automotive engineering), and was specifically made for the S30 Fairlady Z-L and the Bluebird 1800SSS / 1600L models.

According to Kats, even Nissan thougth that the automatic transmission sales was below expectations, so they tried to push the sales. Thats why all major interieur photos in the Japanese S30 sales brochures have switched from showing the manual transmission shifter to automatic gear selector prominently at some point.

In Japan, there were also special advertizing press photos and prints for the Nissan Automatic transmission Fairlady Z cars, like the nice showroom canvas-print below:

Once the Automatic transmission became available in Japan, Nissan issued a special multi-page insert for the Fairlady Z Sales brochure, which again featured various racing drivers to promote the automatic transmission:

He also mentioned that you will most likely find the Automatic transmission in Japan in the HS30-HA version, which is the L24 equipped, G-nose front-end, luxury variant of the S30. It was quite expensive, with high road tax (due to the >2L engine) and only wealthy people could afford it. Those customers usually could afford and often went for all the “bells and whistles” by ordering all options, including things like the air conditioning, vinyl top roof skin, and the automatic transmission.

3.2 Market introduction North America
I wasn’t able to confirm any introduction date for the american market, but my assumption is that it must have been around March / April 1971, just around the time when the change from the 3N71A to 3N71B was made.

In North America (USA & Canada), again, most sub-variants were available with Automatic transmission. The best overview can be found in the 1979 North American / Canadian parts catalogue:

This picture from the nov/dec. 1994 Issue of the Z-car magazine (taken at the 1994 National Z-car convention in USA), shows Mr. K’s special yellow G-Nose 240Z, with a sign that says, it was the first automatic transmission Z imported to the US, in January 1972. This contradicts the previously mentioned 1971 US-market car with a 3-speed transmission, which I test drove (see above). So probably they got the dates wrong on the sign.

And also because the export market service bulletin (including USA and Canada) for the introduction of the 3N71B was released in April 1971.

3.3 Market introduction in other markets
In some factory documentation, the automatic transmission is listed as an option for all export market countries, including Europe (H(L)S30Q). But the local Datsun import companies decided that they only import and sell manual transmission cars. Most probably because “luxurious” and more expensive automatic transmissions were not really demanded for sports cars by the customers. The most cars with Automatic transmissions were originally sold in the north American continent and some in Japan, Australia and maybe other smaller markets, but it’s safe to say that the big majority of S30 cars got equipped with the four-speed or five-speed manual transmissions, depending on specific model versions and markets. That does not rule out that a hand full of Automatic transmission cars ended up in Europe through grey-imports or in other ways. In the later documentation for Europe (approx 1972+) the Automatic transmission section got removed.

Even though the Australian parts microfiches mention that the 3N71B (31020-X0700) replaces the 31000-E8051 (= 3N71A), the early variant is nowhere listed in the manuals. I believe – and this got confirmed by Australian Z-specialists – , that effectively, Australia only got the 3N71B transmission, start in April 1971. Like North America, just around the time the 3N71B got introduced.

As you can see in the following chart from the parts manual, there were different export versions for different market (Those not marked for any specific market are generic export models for smaller countries), but the HS30Q and HLS30Q European models never got the Automatic transmission.

Funny enough, the official Export models parts manuals in some cases mentions that the automatic transmission is exclusive to USA and Canada, which is clearly wrong, as shown here inthe 1974 L-Drive:

This is also confirmed in the 1974 Datsun Service data booklet, But then again, they forgot to mention the 4-speed Manual transmission. As usual, be careful with factory documentation, especially for export markets.

4. Evolution from 3N71A to 3N71B, and further changes
During the lifetime of the S30 Cars, the design of all Transmissions got an an evolution from the early 3N71A to the later 3N71B type. The reasons for the redesign were to reduce manufacturing costs and improve useability and lifetime. Remember: The 3N71A was the first transmission that JATCO ever produced, and they sure learnt a lesson or two in the beginning and quickly came up with an improved version, the 3N71B

4.1 Changes for the 3N71B:
The Swiss Datsun workshop mechanics training documentation shows the differences between the two types:
– Greasing: B-type Automatic Transmission Fluid (ATF) according to GM Specification (A-Type wa according to Ford specification), see table in later chapter.
– Oil filler neck & dipstick: Redesigned
– Oil cooler piping connectors: New position on the housing (20mm higher than on A-Type, not interchangeable)
– Transmission Housing: New 3-Piece (A-type was 4-piece)
– Low & reverse gear brake: Membrane removed and different slats
– Centrifugal governor valve: Now one-piece design
– Parking mechanism: Added two balls for smoother insertion of P-mode gear.
– Different Pinion and drive of speedometer gear.
– Mechanical: Different Brake-band, Clutch drums, Main shaft, Planetary gear sets, Oil pump and valve block.

According to the same documentation, some parts are interchangeable between the A- and B-transmission, but most are not. The whole transmission can be swapped, but also requires additional changes (See following chapters).

4.2 changes during the 3N71B production run
During the production period of the 3N71B transmission itself, again several improvements got implemented, as shown in the Swiss automatic transmission technician training manual:
– From Serial number 106 11611: Different position and improvement (added lubrication groove) of the main shaft bearing in the oil Pump.

– From Serial number 290 3803: Front surface of the rear clutch has improved surface treatment to reduce excessive wear
– From Serial number 211 0078: Drilled holes in the oil pump housing got increased diameter to improve oil circulation flow.

Further changes may have been integrated in later serial numbers, but my documentation is limited to the above data.

4.3 3N71B introduction in export markets (Including USA, Canada and other export markets):
As there is no specific documentation for smaller export markets, it is most likely that the change in all export markets was introduced simultanously to the changes in the North american-market.
The American Parts microfiche book states that the 3N71A Type transmission was used up to March 1971, before it was replaced with the 3N71B Type in April 1971:

4.4 3N71B introduction in the Japanese market
The Japanese parts manual doesn’t mention any introduction date, but states that, A-type Auto transmission was used up to SNR S30-004902

And the first B-type Auto transmission started with Car No S30-004903

5. Transmission Identification
5.1 Transmission type casting
On the automatic transmission, you can usually (but not always) find the type code cast into the case, as shown on the 3N71B transmission in the following picture. Note that the location of the code casting, can be in different positions depending on the Transmission.

Naming key:
3 = Amount of forward gears
N = Nissan Design? (Allthough also used for other car manufacturers)
71 = Space between gear pair in mm (71mm, similar as in the manual transmissions naming key)
A / B = Version / Evolution (A-type, B-type, …)

5.2 Typleplate
At least for the 3N71B transmissions, a typeplate with the the assembly number of the transmission and the Serial number (incl. Production date, see below), can be found on the right side of the transmisison housing. I wasn’t able to find any information regarding the earlier A-type transmission, so it might be possible that this was only introduced for the B-type version.

JATCO Typeplate with stamped specific model and serial number code (Example from a different non-S30 3N71B transmission model):

5.3 Serial Number stamps + Production date
The german 3N71B Service manual explains the 7-digit serial number Key.

1. Digit = 5 = Last Digit of the production year (5 = 1975)
2. Digit = 6 = Production Month: 1= Jan, 2= Feb., 3= March, … X= Oct., Y= Nov., Z= Dec. (6 = June)
Digits 3 to 7 = 12345 = Censecutive production serial number of that specific month (Number starts from zero again with every new month)
Example shown above: 5612345 = Producton year 1975, Production Month 6 (June), Serial number 12345

Interrestingly, the Japanese 3N71B (Not Z-specific) manual mentions a slightly different naming key, with totally 8 digits, and two digits thereof used for the production month (01 to 12). Either one of the manuals is wrong, they changed the numbering system at some point, or used different numbering systems for differnt assembly types.

5.4 Assembly type number
On the Tyeplates lower row, you can additionally find the assembly number, starting with an X and four digits. For e.g. “X0112”. The assembly number refers to a specific sub-version of the 3N71B transmission. for e.g. used gearset, aircooling or watercooling, floor shift or column shift, etc. In the various documents, you can find the technical details and specification of a certain assembly type. Throughout my collection of factory documentation, I was not able to find any assembly number information for the early 3N71A transmission models, so it’s likely that they only introduced it for the 3N71B transmission.
The following list from the 1979 Swiss Datsun mechanic training course manual does not include the S30 models, but shows different 3N71B Models with Assembly type numbers used in other cars, just for reference:

6. Specification of the X0700 variant
To list the detailed specification of all variants would blow up this post unnecessary, so instead, I decided to focus on the most commonly installed (at least in export markets) X0700 assembly variant for the H(L)S30 cars with L24 engine:
In the export market documentation and parts manuals, you can see that the X0700 assembly, is the version used for 240Z (and other, but not all S30) cars.

In the same documentation, you can also find the the datasheets with the specification for the specific models, like the X0700 (Also used in the S30, but not listed in this document from Switzerland, because the S30 was never sold here with an A/T):

In the Datsun Switzerland automatic transmission training course documentation, it is also mentioned that the 3N71B Transmission with the X0700 specification has the internal production name “NL24G”.
This name is never visible anywhere on the transmission, but is sometimes referred to in the technical documentaion.
My understanding is that it means:
N = Nissan
L 24 = L24 Engine
G = Used gearset / specification
-B = Sometimes an additional letter, like L24G-B can be found in the naming, indicating an evolution of the base variant.

The very detailed Datsun / Nissan specification booklet shows the specification of the S30 “X0700” aka “NL24G” 3N71B transmission.

And some more:

Additional information can be found in the service manual but also the specific spare parts catalogue, which lists specific parts for the X0700 (or other) assemblies with exploded views, and other details.

7. S30 Automatic transmission overview.
As it might be a bit confusing with all the different names, variants, assembly numbers, and cars, I decided to make a nice overview, based on the information I have officially confirmed by factory documentation.
It’s a brief overview with focus on the earlier versions of the S30. The S31, 260Z, 280Z and 2+2 / 2by2 versions are not properly represented. But it will give you an idea. I’m also pretty sure that there are more variants which are not visible in my documentation.
Note that the numbering is not always sequential, why it’s sometimes confusing. For e.g. the X0704 was introduced after the X0700, but before the X0702, etc.

Red fields in the table mean that the data is missing or unclear.
X = equipped with
– = Not equipped with

As you can see, for the S30 alone, I found 14 different (!!) variants of the 3N71A/B transmissions. Which is crazy, for such a low-volume optional product. My guess is that, because this was the first transmission produced by JATCO, they quickly learned some lessons and constantly updated it with improvements.
Interrestingly, ALL S30 variants around the globe had the same automatic transmission gearing, despite having different engines, weights, etc. Thie adaption to the car was made solely through the final drive gear in the Differential.
All the above information can also be found in the Datsun / Nissan Specification parts and service manuals. Note that many documentation do not show details about the 3N71A, because it was quickly replaced with the B-Type and not many A-types were installed.

8. Center Console
The center console is of course different than the ones used for manual transmissions, as shown in the following photos:

9. Automatic transmission fluids:
This is oil recommendation for the 3N71A and B automatic transmission, taken from the 1979 swiss datsun mechanic training course documentation:

The Japanese Fairlady Z Operation manuals mentions to use “Elephant oil Nissan Matic Fluid” for the automatic transmission:

10. Swap/ Interchangeability
I’ve had some people asking me if it is possible to swap from a manual to an automatic transmission. Short answer: Yes it is. Long answer: You need to change a load of other parts. The center console, the exhaust with different tube routing for manual transmission clearance, the radiator with additional cooling connectors for the Automatic transmission torque converter, removal of the clutch pedal, different propeller shaft, different oil pan and oil strainer, and longer front suspension springs for the increased load of the automatic transmissions weight, additional wiring for the automatic transmission inhibitor switch and the downshift solenoid, additional “Full Automatic” Emblems on the trunk, different final drive gear for Automatic transmissions and much more. So while a swap is technically possible, i think it makes no sense from a workload / investment point of view. It will be also difficult to source all correct parts required to do it, these days.
In the following photo from the automatic transmission introduction bulletin, you can see two of the mentioned differences. the different exhaust and the additional cooler for the transmission fluid:

11. Maintenance
For maintenance details and description of special Nissan Service tools, please refer to the Nissan factory 3N71A / 3N71B Service manuals (See links below)

In the Swiss Datsun “Warranty lead times” folder, you can see the labor hours a workshop was allowed to charge to Nissan in case of required warranty work.
This gives you an idea of roughly how much time is required for each operation, for a trained and skilled machanic. Note that I only have the data for the S130, but i guess it’s not that different from the S30, so I post it here as a reference:

Nissan also provided a range of special tools to maintain and repair those transmissions. An overview of available / required equipment, and what it’s used for, can be found at the rear of most 3N71A/B service manuals:

12. Troubleshooting
For troubleshooting guidance, please refer to the 3N71A / 3N71B Service manual, too, where you can find a nice overview of issues and how to solve them.
There is also this cool troubleshooting guide slider for the

13. Upgrades
Usually this is not a transmission known to be modified extensively, because most users who own an automatic transmission prefer to drive relaxed. Nevertheless, during my research i came accross a transmission specialist called AL’s race glides in Australia, who offers reinforced billet aluminum oil pans for the 3N71B. It is mentioned that it is for the rotary (Mazda) version, but it might also fit Datsun / Nissan variants of the transmission. But I’m not aware of anybody who had tried this yet.

14. Identification
S30 cars often had markings on the Dashboard frame (where the steering column is attached) or underneath the glovebox liner. We believe they were written there by the assembly-line workers to identify the specific assembly variant of a car in the line.
Cars that were equipped with an automatic transmission from the factory, often (but not always) have these Katakana marks: トルコン, which translates to To-Ru-Ko-N = “Torucon” or “Torcon” and used to be a period slang term in Japan to say “Torque converter”, which again stands for Automatic transmission.
Here are two examples that roughly translates to “Austro Torucon”, which means these cars were originally Automatic transmission equipped cars, designated for the Australian market.

15. Original Ressources
There is a big range of factory documentation and service manuals available in various market versions for the different transmissions. Aside from the standard S30 FSM and Parts manuals of course, which should always be the starting point for any research.

Some of the documents are available for download here:
– Datsun – Service Manual – Full Automatic Transmission – 3N71A
– Datsun 3N71B Service manual

15. Conclusion
It’s safe to say that S30 cars ordered / delivered with automatic transmissions were a niche. I don’t have any numbers for this, but my guess that the percentage of all delivered cars with automatic transmissions is in the single-digit area.
At the time when Automatic transmissions started to be actively sold in various markets, the second version (3N71B) got introduced, so this means that cars delivered with a 3N71A transmission are quite rare, but again, i don’t have any numbers, and they definitely DO exist.
At a time when most people were driving manual transmission cars, the “advantage” of a modern automatic transmission somehow didn’t really fit with the sportiness of the Z cars, while the same (allthough slightly different specified) transmission was used broadly in all kind of cars of all kind of manufacturers.
Overall, the Automatic transmission option for the S30 cars is a surprisingly “fun” transmission to drive in a sports car, but as said – will remain in a niche in the 240Z / S30 cars history.

Thanks for reading, I hope you enjoyed it, and thanks especially to the entire team (Gavin, Kats, Alan, Florian) at S30.world , and Heiko for providing me some of the missing data and useful inputs.