Ok, so recently I had the 5 speed out of 240k sedan because the shift action had become pretty sloppy and 5th gear would not stay engaged without holding the stick in position.
The rear seal was replaced and the shift mechanism was completely removed and seal replaced which requires the box be pulled apart. That was sent to a local engineer that replaced the shift pin and made up a new cup for the bottom of the stick, beautiful........Feels so much better!!

Also, the reverse light had stopped working completely but I had a new switch installed only a couple of years before. Turns out it was the sloppy shift that was causing the lights not to work this time.
What was interesting was the fact there are 3 of these gearbox switches screwed into the side of the gearbox, all corresponding with each of the 3 gear shafts.
My question is, what the hell are the other 2 switches for? The wiring for all disappear into the loom so I can't trace them, and when I checked out the wiring diagram in the back of the workshop manual, there is only a reverse switch shown.......huh?

If one of you brainy Datsun blokes could please enlighten me I would be forever in your small yet significant debt

Depending on the model year, there may be top gear switch [4th] for an emissions function, the reverse lamp switch and an O.D. gear switch [5th].
These are all present on the Bluebird 5 speed, which also uses the FS5W71B.

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Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Is the center plate cast iron or aluminium? If aluminium then I would say its a bluebird and that's why it has 3 switches.

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Chris Thomas

1971 1600, mild L18, 5 speed

All I want is less to do, more time to do it and higher pay for not getting it done.

Yes, but the question was related to the wiring that is attached to the switches, so the car must have a requirement for them.

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Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Afaik the only switch used on the 240k manual trans is the Reverse (Backup) Switch. The wires used for this are Red and the other is Red+Blue.
The other two pairs of wires are not used...

Thanks for the replies guys, much appreciated.

There is obviously a reverse switch that is wired in and the fact that the other two identical switches are also wired in, grouped with the reverse switch and feeding into the loom tells me they serve a function. My guess was something to do with emissions also.
What I don't understand is how they are not mentioned or detailed in the main text of the workshop manual for the driveline or emissions sections, or even in the wiring diagram......?

As per Nissanman's reply, if one switch was for a 4th gear emissions function, what would that function be, also for the overdrive function?

My car on a trip seems to use more fuel than what others have told me these cars were capable of, if there is an emissions issue which is causing this, I'd like to sort it out.
A recent trip to Adelaide from Mildura in the heat wave before Christmas saw a range of approximately 500 to 540 km for the 60 litre tank.
That's sitting on 110km per hour with the air-con on, 4 people in the car plus luggage.
Fuel used ranged between 11 to 12 litres per 100km or 9.06 to 8.3 km per litre.
US Miles per Gallon worked out between 19.6 and 21.4. It was suggested to me that they are capable of 30?

Condition of the motor always makes a difference of course and my car is an original uncorked motor with almost 160k on the clock. It does puff a bit out the pipe if you give it a rev but there is no visible smoke at idle or low revs, compression is good and it starts instantly, idles well, revs cleanly.
I run Penrite HPR30 Full Zinc in the motor and the gearbox and diff oils are 3 months old with an oil conditioner added.
Basically I'm doing everything I can to make sure the old girl is as happy as possible

The fuel use sounds heavy to me as I used to drive (15 years ago) a 307 chev powered Holden HK Brougham with a Powerglide and 2.78:1 ratio LSD that returned up to 18 mpg on a trip.

Any thoughts guys?

There might be a separate Service Bulletin to cover these switches in your model car.
Here is what I found in the S1/S2 Bluebird FSM: - The top gear switch/O.D. switch is connected to a Vacuum Switching Valve.
It modifies the vacuum signal that feeds the vacuum advance motor on the distributor.

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Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Ahah.....thanks very much for that NissanMan. I will have a look at my car and see if we have the same set up.
Cheers

Hey guys, I have another related question with the 5 speed box.

For as long as I have had the car, if you want to use 5th you need to hold the gearshift in place or the torque of the motor will throw it out of gear.
When we had the gearbox pulled apart we inspected the gears and rails and bearings.....all seemed to be in top condition.
I understand that on each cluster there is a ball and retaining spring that can be accessed from the outside of the box and that the tension of the spring can have an effect on the shift action but does it also hold the shift in place and therefore the gear selected?
I removed and inspected the spring and it wasn't broken but I don't know how stiff it was meant to be.

Am I on the right track here guys or is there something else going on with 5th gear in my gearbox?

Cheers,
Hayden.

Looking at the flow chart for "Gear jumping out of mesh", the first item to check is wear/fatigue/play of the front and rear engine mounts.
The next culprit is "Check end play of "jump out gear"".

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Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Ok, so not what I thought then, I guess the spring is simply for shift action feel?

Next related question then. We have purchased a 280zx 5 speed car with the view of using the gearbox for my 240k, would it be the same unit and a direct bolt in or are there differences? The zx is a 78 car.

Well, it would be a FS5W71B 'box and from my Haynes, the ratios should be: -
1st..3.321 : 1
2nd..2.077 : 1
3rd..1.308 : 1
4th..1.000 : 1
5th..0.864 : 1
Rev..3.382 : 1
Speedo drive 17/6.

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Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Is the nut on the back of the main shaft tight ? That's the main issue with 240K boxes that I've seen and will cause them to jump out of gear in severe cases. Or there's a problem with the forks/selector hub.

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Happiness is watching the race.... in your rearview mirror

Yes, the 280zx box will bolt straight into a 240k

Your "high" fuel usage,,,, lets see, 4 passengers, luggage, aircon, and 110kmh, yep that'd do it, diff ratio prob a 3.9 or a 3.7.
The Holden308, barely ticking over above idle, a 1:1 top in the Glide, AND a 2.7 diff!

They can get 30 to the gallon, but pump tyres to 40psi, dith the passengers and ALL luggage, and unnessarcary stuff, and sit on 80 kmh ( USA 50 mph, where speed limits used to be 55 mph)
You'll get that 30 mile per gall then!

Jumping out of gear due to the dogteeth and or syncro teeth have excessive wear, and there'll be a bit of excessive end float on mainshaft. She's not young any more!

The ball detent springs on centre plate, are purely for the detents on the three shift rods, just to more positevly locate the neutrals on the rods, when in any gear, the ball and spring is pushed out.

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Yep, i race a Datsun, and I drive a truck, sometimes I get confused, and then the truck goes fast, and the Datsun gets a lot of boxes shoved into it. AWW GEE