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Discussion Starter #1 (Edited)
This is now probably the 4th or 5th time I've begun typing this. Every time I begin to type, I realize that I've got so much more that I want to type, and it ends up evolving into an entire essay. Over the last 2-3 years, I've received a few messages from racers asking me about D-series transmission setups. While I have done relatively recent work on D-series transmissions (research wise), I haven't really posted about them since about 2005-2007.

That was ~15 years ago. Too further complicate or date things, its been 21 years since the last D-series SOHC transmission has been made (I'm not counting the Europe / Asian D-series variants which are entirely different transmissions), and I'm also not counting the 2001-2005 D17 transmission, which appears to be somewhat of a CCW, 'mirror image' version of the 1st gen insight transmission).


So be that as it may, there are a few things we need to take into consideration:
  1. Drag racing with this transmission / D-series platform is stupid. If you're making lots of power with a turbo D-series engine, look into getting a 1st gen HR-V transmission from Europe and convert to that transmission. They are cheap and they bolt up to your engine. Heads up: they are cable shifter and you will likely need to modify your cross-member. Its basically a SBXM 1st gen CR-V transmission, so B/H-series (See my B/F/H transmission post here: Honda B/F/H-Series Transmission gears interchange. B-series AWD - CR-V SBXM - Honda-Tech - Honda Forum Discussion)
  2. The 1988-1991 Cable DOHC ZC transmissions / gears are going to be near impossible to find. I would be surprised if any JDM engine importers had any of these transmissions still.
  3. Aftermarket final drives are still available, and I've yet to hear of anyone having issues with the Gear-X or MFactory final drives. (4.53, 4.73, 4.93)
  4. MFactory / Gear-X still offer a close-ratio gearset which provides 3rd / 5th gears and is a good option if you've already got a 1.894/1.900/1.909 2nd gear and 1.250/1.259 3rd gear. These are essentially 88-91 LX / DX / EX / Si transmissions, or 92-00 EX / Si transmissions
  5. Used, junkyard D-series transmissions are cheap and they're still available in USA. Which means, that its still relatively easy to obtain final drives (3.722, 4.058, 4.250, etc)
  6. Despite these obstacles D-series transmissions are still one of the easiest transmissions to build, because of the broad span of gearing that Honda offered in these transmissions; (1989 CRX HF's D15B6 is 62hp, 1999 Civic EX's D16Y8 is 128hp), if you do your research, you can build a true, close-ratio 2-3-4-5 transmission that mimics the characteristics of true racecar gearing for very cheap.


Okay so now that we've got that established, there's another statement that I want to declare;
Your 1st -> 2nd shift doesn't matter. As mentioned you shouldn't be drag racing these transmissions. Especially from a dead stop! The only scenario where I can see that 1st -> 2nd shift matters is if you were a courier in a city and if you did a ton of driving between stop lights. If you really care about this, run the MFactory/Gear-X 3/5 kit and use a EX 1st/2nd, and possibly one of the 3.083 Gear-X first gears that I convinced the world that we needed back in 2007
(Side note: I don't receive any monetary gains by you purchasing this, so it doesn't matter to me.)

With that out of the way, here is a simple formula that I use in all of my own transmission tables in my spreadsheets that I use to quickly assess the spread between the 2-3-4-5 gears. I will call this value 'Q', The formula for Q is very simple.
2nd gear / 5th gear = Q

Examples:
Q = 1.909 / 0.702 = 2.72 - 1996-2000 Civic EX
Q = 1.761 / 0.702 = 2.51 - 1992-1995 Civic DX
Q = 1.944 / 0.878 = 2.21 - 1988-1991 Cable DOHC ZC

These numbers are the most significant here, because they tell us what the spread is between the 2-3-4-5 gears. What we want to do is lower this Q number (almost) as much as we can. We want to tighten the 2-3-4-5 spread. In other words, we want 2-3-4-5 to be closer-ratio.
Because of the fact that Gear-X / MFactory offers higher ratio final drives, we have the freedom to use a gear-spread that, while close, it might normally be too "tall" or "long" to be desirable in a performance application, and then just use a higher ratio final drive to bring the gearing to a useable range for our performance application.

In a nutshell, what you're wanting to do is use a longer (lower ratio) 2nd gear with a shorter (higher ratio) 5th gear. How does this translate?

Consider the following setup. D16Z6 transmission with ZC 3rd, VX 3rd as 4th, and ZC 5th. Again, these ZC gears are very difficult to find now:
Code:
1st - 3.250
2nd - 1.900
3rd - 1.346
4th - 1.066
5th - 0.878
Final = 4.25

Q = 1.900 / 0.878 = 2.16
This Q value is pretty good. Its the same Q that a 2017+ FK8 Civic Type R would have if they were to run one of my 4-5-6 gearsets (shameless plug, lol). But there are actually lower Q values that we can achieve using factory D-series gears.

Take a look at this setup for 1988-1991 Cable transmissions
Code:
1st - 3.250
2nd - 1.650 (88-91 HF or STD)
3rd - 1.172 (92-95 dx/lx, 96-00 cx/dx/hx/lx - this would require light modification. Same as when using ZC 4th in 92-00 trans)
4th - 0.937
5th - 0.771
Final = 4.93

Q = 1.650 / 0.771 = 2.14
How do these transmissions compare?
Orange = D16Z6 with ZC 3rd, VX 3rd as 4th, ZC 5th
Purple = Cable Frankenstein D with 4.93 final drive.
137725
 

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Formerly weebeastie
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1,067 Posts
The only source I've had for ZC gear sets in the passed 5 years is the occasional DOHC ZC trans showing up on a for sale post, or from down under. They apparently still have a decent supply of DOHC ZC stuff floating around AU/NZ. Great write up. Its been a while Bense. Guy who talked me into my first F2D. Back when the forums didn't suck and things were crazy. Good to hear from you.
 

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Brokedick Millionaire
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HF 1-2, ZC 3-4-5, 4.25 RD, 21" tire.

SCCA racing trans, rolling start in long second gear, then go into close 3rd gear without power drop and jump 3-4 cars before first turn.

 

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Discussion Starter #5
HF 1-2, ZC 3-4-5, 4.25 RD, 21" tire.
That requires these unavailable transmissions:
  • 1988-1991 4-speed / HF parts -
  • 1988-1991 Si / Ex final drive -
  • 1988-1991 DOHC ZC gears

Here is MFactory 3/5 on D16Z6 trans with a 3.7222 final.

Requires:
  • 1992-2000 D16Z6 or D16Y8 trans
  • 1996-2000 D16Y5 or Hatchback final drive
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Brokedick Millionaire
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40,603 Posts
1990-91 EX FD is 4.058
HF/STD are great donor transmissions, esp. for shifter forks.
Last set of ZC 3-4-5 I bought was $425 shipped.

On that note, I need another STD/HF 1-2 for a customer in Canada....

Also, have you ever though about using a hydro inner case and a cable outer case?
 

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Thanks for the information. Just swapped a z6 tranny into my hatch for the fun and wow what a difference, going to look into the combo's you mentioned for the actual build.
 
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