4-speed or 5?

Ah yes! we’re talking transmissions today.

The Datsun 280z came with two manual transmission options in it’s lifetime: the 4-speed and the 5-speed (for which the car is also badged noting the upgrade). And after driving the 4-geared ’77 280z for nearly two years, I’m kinda at that point: I want more gears! :]

But wanting is often different from needing, and we just need to build a case to bridge the two. Call it, justification through research – let’s do it.

Here are the gear ratios for Datsun / Nissan transmissions at the time*:

’74-’78 280z 4-speed:
1st…. 3.321
2nd… 2.077
3rd…. 1.308
4th…. 1.000

’77-’78 280z and first year ’79 280zx 5 speed:
1st…. 3.321
2nd… 2.077
3rd…. 1.308
4th…. 1.000
5th…. 0.864 (13.6%)

’80 280zx 5 speed:
1st…. 3.062
2nd… 1.858
3rd…. 1.308
4th…. 1.000
5th…. 0.773 (22.7%)

’81-’83 280zx non turbo 5 speed:
1st…. 3.062
2nd… 1.858
3rd…. 1.308
4th…. 1.000
5th…. 0.745 (25.5%)

As you can see the ratio drastically changes in the ’80 280zx 5-speed when going from 1st to 2nd. Additionally, the ratio of the 5th gear gradually moves further from 4th’s 1.0 ratio as the years go on (differences noted by percentage changes).

With regards to the first difference mentioned, the change to 2nd gear really depends on driving style and fuel economy needs. A taller ratio in 2nd (closer to 1.000), will require more power, higher RPM, and thus more fuel. Gears 3 and 4 are ok because we’ll be moving quite a bit at those gears, but 2nd is tricky. Spend more time in first, or bang through gears?

For me, I actually spend a lot of time in 2nd. I usually take back roads for my commute, and time out traffic lights so i’m rolling into the green. So it’s natural to use 2nd to get the rolling 280z moving again (deeper than that, I’m terribly used to 2nd because i swear we used to have to start my brother’s 510 in 2nd gear – 1st was kind of wonky…though he says it was never that way hahaha).

So just by looking at the gearing, we can see with the early Datsun 5-speeds we’ll get better proportioned low-end, but not as tall on the top-end. Now that we’ve decided on a 5-speed…what are our 6-speed options? :]

Data specs from Ratsun post, DatzenMike, 09 July 2012.

2 Replies to “4-speed or 5?”

  1. Hey justin great post about gearing!

    My monkey-motion 4 speed in my S1 had a bearing fail on me so I did the whole 5 speed and differential swap. I chose the zx 81-83 n/a tranny because I much prefer a close ratio to the predecessors’ wide ratio nature. It’s definitely more engaging on windy roads plus the r200 diff I swapped has the taller 3:90 gears from an 81-83 zx n/a. Don’t forget the rear end ratio will also affect your choice in transmission. By the way I also have a liking for 2nd gear especially for rolling stops and starts.

    Check out my past posts in my friend and mine’s car blog to see some of the work if you’re interested.

    Also, I have never looked it up so don’t quote me, but a dude i know building a 600hp turbo zx told me he had been researching a mod that could be worthwhile. He talked of modifying a bmw 6 speed manual tranny to use an L-series bell housing to use in his zx. Kind of extreme, especially cool, and worth a few minutes of investigation I think.

    – Jon Tong

    1. HEY JON!
      wooo that’s definitely something i over looked – diff ratio! I’ll have to find out what i have under there…

      that 6-speed with L-series bell housing sounds super fun! i just read someone else doing it with a mazda mx-5 6-speed too..

      i’ll certainly check out your posts about the work. hey and also too we’ll have to find a time to do a ride!

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