The forks are steel. It could be a good basis for a close ratio conversion. It would involve making a new input and drop gear but I don't think anyone would want to spend $1800 on a 56a synchro box.

Be warned, there is going to be a flood of photo's coming in as I have taken a fair few pics of this box and it is already set for reassembly at work. As it turns out it is in fantastic condition. It will also go up for sale at the end of the thread. I have spent about 2 hours alone cleaning the bastard casings.

this makes me want to get a bench so i can give my spare box a good going over before it goes in

Here are the main differences between the 56A four-speed and the original Datsun 1200 box (56L).

* F4W56A: fitted to all B120 utes. Adopted to all B210. When Japan production switched to B210, export B110s from APR 1973 were supplied with the 56A.

* Strengthened gears: Although there is no change in the gear ratio, each gear has an increased width by 0.039 to 0.079 (1 to 2 mm). For this reason, gearsets are not interchangable between early and late transmissions.

* Strengthened bearings: the countershaft, front bearing and main shaft bearing are strengthened. front countershaft bearing changed from ball bearing to needle bearing

* Improved lubrication performance: To ensure proper lubrication in the rear extension bushing, an oil dam is installed in the center of the extension.

This is something I wanted to ask Don that DD mentions.
The gear width increase from 0.039 to 0.079 (1 to 2 mm)
can these gears be strengthened further in theory with
a further increase width? Could a 56 series box with its
smaller distance compared to the 71 series be made up
with stronger quality and thicker gears?
Also is it possible to have better quality strength input
and layshafts to make a difference?
They are only theoretical questions but Im curious in thinking
that could it have been more expensive for nissan to have used
stronger better quality components in upgraded 56a boxes than
use standard quality metallurgy constructed 63 or 71 series designs?

Hmmm. There is only so far you can modify a gearbox before you are wasting time and money. Besides, we see motorbike gearboxs with bigger gears than a 56a.

Time to remove the selector rods. Remove the detent screws, balls and springs. Only one roll pin on the fork and slide the rods out.




Soft hammer on the output shaft and layshaft and remove both together as the layshaft gears will foul against the dog gears if you are not carefull.




Now it gets layed out on the bench and ready for final dissassembly.

Input shaft off. So I don't mix up the synchro rings I will initially mark them with a pen ao as not to mix them up. The input shaft on these models does not use a circlip to retain the bearing, so to prevent the input shaft bottoming out it uses a thrust washer in between the selector hub and input shaft. A single 3mm ball locates the thrust washer. Budget and efficient old school stuff really. Not high torque stuff really.




No circlip retains the 3/4 selector hub oddly enough. Once the 3mm ball is removed the hub will come off and so will 3rd gear and bearing. I also mark the hub, and later engrave it so that it all goes back together in the exact same way.




Now the press sissors go onto the rear bearing for safe removal.




And once removed will expose 1st gear. Behind the bearing is a thrust washer which also doubles as a gear height shim.

Now that 1st gear is off, the bearing and bearing sleeve are exposed. Pressure on the selector hub will coax the sleeve off. Once again, everything gets marked with the pen, and later engraved.




2nd gear now falls off and you have a dissassembled gearbox ready for cleaning and inspection. Let the cleanup begin.... Sh!t!!! I forgot how I hate this part.




I should point out that it took approximately 1.5 hours to dissassemble the gearbox entirely without encountering any problems.

All cleaned up and ready for inspection. A good starting point is if your gearbox has a magnet, see what is stuck to it. It will give you a good indication of what you expect to find.




Bearing inspection is fairly obvious, and in my opinion, they dont need to be replaced for the hell of it, sometimes a repair can be just fine. But for the sake of $70 odd I'm not going to bother with an inspection, I'm just replacing them all. After all, i am rebuilding it, not repairing it.

The gear dogs and leads should be burr free and have nice points, not rounded shoulders.

As you can see, I am holding the syncro ring in place on the syncro cone. A nice even gap should be visible and when pressure is applied it should no rock or give any indication that it is bent. 100% surface contact is what you want. Note the gap, The service manual of the gearbox should give you an idea of what the tolerence should be, smaller boxs like this are usually around 0.7mm to 0.9mm, but as long as the ring grips firmly to the cone it will work o.k.




I'm checking the gap and I have found the measurement to be 0.83mm. There are no serious signs of wear and everything looks and feels good. All 4 gears vary but are consistent within 0.01mm. Very nice. I usually see 2nd wear fastest and I would be suspect of anything measuring below 0.6mm.

So this gonna get finished don! Good read to! Wouldn't mind trying it myself as might need to rebuild my 71's a few time I dare say