240Z Project

240Z: Transmission and Differential investigation and upgrade options

Istead of fiddling around with all the small bits and pieces i decided it’s more important to get the subframe parts ready so i can assemble the car back to a rolling chassis once the shell is completed. The reason this has been a bit on the low-end of my priority list was the fact that i just had no clue what to do. But lately i read a lot and now i’m even a bit more confused. Same goes for the suspension which i will dedicate a separate post to soon.
The main problem beeing i have a EUROPEAN 240Z, which suspension- differential- and transmission-wise is totally different than US-Versions and therefore useful information is rare and sometimes appears to be wrong. Ask three people and you will get three different answers…
I cannot confirm any of this Informations but so far what seems to be the right data (maybe someone can confirm?), is this:
Differential now:
I’m running a 1972 EU-Spec Datsun 240z. It seems like all 240z’s worldwide have been delivered from the factory with the R180 Differential (Anybody knows the original manufacturer / designer of these?). European-spec cars seemed to have a 3.9 Final drive (Ring gear).
P1030756 - Kopie

The good thing is i will be able to confirm this, as soon as i take my Differential apart and read the numbers on the ring gear (Picture shows a 49/12 = 4.08 Ring gear, not from my car)ringgear.jpg~original - Kopie

Differential Future Options:
Now it seems like i have many options:
– R180 Stock differential, with upgraded LSD (OS Giken, Nismo, Quife, Cusco, ….)
PRO: Direct fitment, lighter compared to the R200
CONTRA: Depending on the original LSD relatively weak and oldschool design
– R190 Differential (Option from various Competition catalogues, Nissan Z432, etc)
PRO: Direct fit
CONTRA: Relatively rare to find.
– R200 Differential
PRO: Widely and cheap aviability, quite Powerful.
CONTRA: Relatively heavy, extensive modifications needed on the stub axles.
– R180 Subaru Differential
Pro: More modern design and quite a lot of parts available, Lightweight
Contra: Again a lot of modifications needed on the stub axle side.

Transmission now:
Comparing images, datasheets etc, it seems like my car came with the first generation FS5C71-A type Transmission. Definitly i have a 5-speed manual like all european cars and according to the cast-design of the housing it must bee an A-Type (First version), But i’m still not sure on that one. Can anybody confirm this?
P1030723 - Kopie

The similar 5-speed transmission from my other 1972 240Z:
P1080531 - Kopie

According to some information on the Interwebs it seems like these are my gear ratios (Still need confirmation on this one):

1.         2.957
2.         1.858
3.         1.311
4.         1.000
5.         0.852
RearGear   3.900

Transmission Future Options:
Similar to the Differential i have a bunch of options.
– FS5C71A (Keep it stock)
PRO: keep it original
CONTRA: Oldschool design
– FS5C71B
PRO: Slightly more modern design
CONTRA: maybe slight modifications needed? (Shifter kit?), Small advantage compared to stock
PRO: Most modern design with much better synchronization etc.
CONTRA: Modification of the propellar shaft needed, etc.

Since i’m planning to run a modified L24 or L28 for street use and the annual trackday, i’m really not sure which option is the best for me. I don’t want to run any overkill setup with huge heavy differentials and a gearbox with a lot of modifications needed for installation, but since i’m planning to take apart everything anyway, it would be great to upgrade it at the same point. So i’m really thankful for all information i can get from the pros. Let me know your opinion.


  • Gavin Doolan

    Hi Nils,
    That gearbox is indeed a 71A type 5 speed from the looks of it. It was fitted to earlier cars with the early style console. The gearstick actually came out a bit further back than the later 71B box did (when they revised the console).

    These gearboxes are good, they were used behind the Skyline (C10) GTR and the PS30 (432) and PS30-SB (432-R) respectively as well as export market 240z’s like Australia. the gear ratios are good and it has a Porsche style synchro set up. The only real negatives are that parts are getting a bit harder to find now if you need to rebuild it and the driveshaft (flange type) is also harder to find now.

    I don’t know what year your 240z is? I’d say it would have to be 71 (maybe late 71 to still have this gear box fitted)?

    As for diff options that is up to you but an R180 LSD would be fine with a relatively mild L28, the r200 is heavier and you would need the components to switch it over, might be harder to find in Europe. Personally I’m going for a 4.1 or 4.4 diff in my 240z with this gearbox.

    • JDMjunkies.ch

      Hi Gavin, YOu’re the man 😀 Thank you so much for your feedback. You confirmed my thoughts. The FS5W71A Seems to be the “best” 1st gen version while the R180 with 3.9 Ring gear seems to be a good option.
      I have two driveshafts and other components, and since it was standard in Europe and i know my sources it’s probably not too hard for me to find replacement if needed. Also i found several sources offering rebuild kits for this transmission. Still not hundred percent sure which route to go but i guess an R190 or R180 with OS-giken LSD and a reworked FS5W71A Would be the best option, sinec the FS5W71B probably doesn’t have the great gear ratios.
      Still have to think about it but you already confirmed my thoughts. THanks a lot man, i really appreciate!!

    • JDMjunkies.ch

      Oh btw i forgot. I own two 1972 (one built in late 1971, one built in may 1972 or so) Z’s. Even if it has the “Gen II” Body it seems like the transmission was never changed or probably later to the “B”-type.
      BTW: Do you know where i can find a manual of the transmission? Who was the manufacturer / Designer of it?

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