Mystery Transmission

[Rocketmann88]

https://photos.app.goo.gl/Tec11coe19iooqvv6

 

I bought an unfinished 240z project 15 years ago that came with a datsun 5sp. The guy told me it was a competition 5sp, but a modified driveshaft³ was needed to fit a 240z. I read many articles, but I still can't find out what it is? What throws me off is the long tail, different casing and the flange that hooks up to the driveline.

 

Help me solve this mystery...

[datzenmike]

FS5C71A

 Originally for the Roadster with competition 'C' Porsche  steel synchro rings. The front bell housing is removable so when the 240z came out in '70, an L series bell was produced so this 5 speed could be used in it. It was never an option in N Am for the Roadster or the Z car but I think was available in Europe*. If you had the cheese you could buy and import the bell fitted to a Roadster transmission to convert it for use on the L series. The one below is a L series conversion.

 

* going from memory

 

 

 

L series bell housing...

[Stoffregen Motorsports]

If it's in good shape, it could be quite valuable.

[Rocketmann88]

The odd thing is that the tail looks different from the pictures for a FS5C71A?  It seem rather long? Did the European versions trcome in differnt cases? It seems to be in great shape.

 

 

[datzenmike]

I'm guessing it's 31.5" long????

[Rocketmann88]

Not sure where I would measure, but from the bell housing to the end of the tail is about 31 inches. If you count part of the bolt on flange, it would be 31.5 inches.

[Stoffregen Motorsports]

3 hours ago, Rocketmann88 said:

The odd thing is that the tail looks different from the pictures for a FS5C71A?  It seem rather long? Did the European versions trcome in differnt cases? It seems to be in great shape.

 

 

The ribs on the tail housing - I seem to remember the competition transmissions having those ribs.  Competition 5 spds have different ratios than the road going counterparts. If you put a clutch disc on the input shaft and marked it, then went through all the gears, counting the rotations at the tailshaft, you could come up with the ratios.

[Rocketmann88]

Mike you were right it was a FS5C71A.  I found a drawing from a JDM site that matched my transmission. This was a non-us unit that was shipped here with the modifications for a 240z. It said the "C" indicates steel syncros.

 

Stoffregen Motorsports, I did what you suggested and found the following ratios:

 

1 gear.     1-2.85

2nd gear 1-1.80

3rd gear  1-331

4th gear  1-1

5th gear  1-.83

 

Maybe not exact, but close. I used masking tape on the flange and clutch disc.

 

 

Now I got to figure out either to use it or give it to someone who can be utilize it more?

 

Big thanks to Mike and Stoffregen Motorsport. 

[datzenmike]

 Your measurements were spot on. For the Roadster...

 

1st..... 2.96..... % change

2nd... 1.855... 37.3%

3rd.... 1.31...... 29.4%

4th.... 1.000... 23.7%

5th.... 0.85..... 15%

 

Used on a 2.4 liter 240z this really favors racing use where the 2.96 first is only a problem starting and leaving the pits. The stock 240z first was 3.952. That's a BIG 21% loss of starting torque. If running a 3.90 differential in a 510 it would be like changing it to a 3.20 gear. Even on a very light 2,100 pound 510 the L16 will be working at every clutch engagement at the lights. Only in 3rd gear in the 510 will the Roadster 3rd gear be the same and of course 4ths are always the same. 

 

 

[Rocketmann88]

Sounds like this transmission woy\uld not working in my situation? Too bad it looks to be in great shape? Who do you think would be interested in this unit?