Close Ratio 71C gearbox

Restores, Revamps and Repairs
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mikec(nz)
Z Club Member
Posts: 189
Location: Tauranga, New Zealand

Close Ratio 71C gearbox

Post by mikec(nz) » Sat Jan 29, 2022 5:38 pm

First if you want an understanding of upgrading the gearbox in your L6 from a 71B to a 71C, either in your 240Z or in my case 240K, this is probably the best information currently on the net viewtopic.php?f=6&t=143&p=40473&hilit=71c#p40473

And some good info here http://datsun1200.com/modules/mediawik ... p?title=71

I did this upgrade and despite running around 250rwhp have not managed to break it. The size of gears from the 71B to the 71C is dramatic. They are rated to around 300hp/300torque I think so should handle anything a l6 can put out (fancy twin cam heads excepted).

If you want to see the photos of the install check this out viewtopic.php?f=34&t=4467&hilit=71c+240k&start=30

So after nearly five years of running and with the new engine, really noticing the gaps between the gears and it is dropping off the boil between gear changes.

So started investigating a close ratio kit.
It turned out to be a lot harder than I thought, everyone seemed to say they were no longer available.
However over Christmas I sent an email direct to kameari engine works and they were very helpful and wrote good English.
So last week this arrived
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The only problem is the 5th gear, was not available. There is a post on their facebook page saying they are working on it but that was in 2020 and when I enquired I was told However, the 5th gear is not yet completed. It will take a long time to complete.

So I proceeded without it.
But more on that in the next post.

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Grunzter
Posts: 541
Location: Epsom, Auckland

Post by Grunzter » Sun Jan 30, 2022 7:29 pm

Wow, good stuff.
I have bought a few things from them also, very good to deal with.
SO you will use the current 5th gear?
Is that an overdrive?
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mikec(nz)
Z Club Member
Posts: 189
Location: Tauranga, New Zealand

Post by mikec(nz) » Sun Jul 16, 2023 1:23 pm

Oops sorry forgot to update this post. I have built the gearbox and race tested it - great stuff. Close ratio is nice and the stronger 71C kit is holding up to punishment so far. Don't see any reason for it not too in the future. So we had some issues with parts. 71C gearbox are not that easy to find, and then you also need to get the different input shaft. The Silvia turbo gearbox provided the correct kit - nice and thick and the old 300ZX or early skyline provide the input shaft and of course this was combined with the Kameari close ratio kit. So that all went together nicely with help from Driveline Automotive in Rotorua.

I also did a shortshifter kit from Les Collins Racing in Australia.

For the 5th gear, as Kameari could not supply a close ratio (they are planning but could not provide a date - they said "It will take a long time to complete.") so I did some searching. Stock 5th gear ratio (or overdrive) for the datsun boxes is 0.76, but the Kameari one was going to be 0.84.

I found that in the USA some Nissan gearboxes came with variety of 5th gear options and the Nissan trucks had a lower 5th and that All State was remanufacturing them (I assume they machining them not forging them to save costs). Did the research and purchased part number "NIS-5B" FSW71 5th gear kit. They would not send to NZ, but got it sent to a mate in the USA, who forwarded it on to me. I got a spare as well just in case as they were only $82.10US (in 2022).

Here is their range, but a great option to get a better ratio on the 5th gear for a cheap price.

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