Hybrid gearboxes. In search of the perfect gear ratios.

[007]

I've never done it, so I can't say for sure. in theory it isn't hard at all. just a little tricky. change 1, 2 and reverse as a set, then 3rd gear, and retain 4th, 5th and the FD.

[BETEK]

Shafts of 1992-2000 D-series manual transmissions

Main-shaft (gears in order)


As you can see 1st and 2nd gears are included on the main-shaft and they can't be separated



Counter-shaft (gears in order)


Counter-shaft without the gears, the gear that is shown as part of counter-shaft is the gear that transfers the motion to the final drive gear.

[saxophonias]

So changing the final drive means changing the same shaft too, right? Does the main shaft has to be from the same box the final drive is from?
Is the following mix possible?

d14a4 gearbox with 4rth 5th and final drive from d14a8

[BETEK]

In order to change final drive in D-series 92-00 what parts inside of transmission we have to change.
Final drive gear and counter-shaft only?
Or something else too?

Do the main-shaft need of changing when we changing the final drive?

[saxophonias]

Ok it seems that we have come to some conclusions regarding what can or can't be done. It seems possible to swap the 4rth 5th and final gear from an a8 gearbox to a d14a4 one.
Look at the boxes and compare
stock a4 and a8 box


hybrid


I have set the rev limiter to 7000rpms which is the most likely to be as I have seen in the various dynoruns I have taken part in. If you set it at 7200 which is what we see on the dial, the results aren't consistent as far as I can tell.
This is from Betek which he did so


If you pay close attention to the hybrid box it seems good enough as for the speed for its gear but a bit worried about the the gap between 3rd and 4rth which is going to be bigger as it is now at the stock a8 box.
Also i think the results for the revs each gear drops are inconsistent. So I am a bit confused

[saxophonias]

this is are some videos from d13b gearboxes
http://www.youtube.com/watch?v=ti1WhxoXWsg
http://www.youtube.com/watch?v=5DQbEHw6psU
http://www.youtube.com/watch?v=P88SnBdDxj0

[Sebastix]

This is video from a N/A D15 with a D15 gearbox with the 3rd and 4th gear of a CRX (same gearbox setup as mine)

http://www.youtube.com/watch?v=GMp0UOl6MoE
http://www.youtube.com/watch?v=ScknMnImqCc

[pardizzle21]

Any info on d15 import s20 gearbox?can get one for £250, factory LSD and 70,000miles.
Sounds like a bargain to me!?

any help apreciated

[pioootr]

In my opinion perfect gear ratios (as the title says) are:

• Street car
  FD - 4,25 or 4,4375
  I - 3,25
  II - 1,9
  III - 1,25
  IV - 0,9375
  V - 0,75

• Race car
  FD - 4,4375
  I - 3,25
  II - 1,944
  III - 1,346
  IV - 1,033
  V - 0,878

By perfect I mean equal gear spacing (the amount of torque you loose)
So the first selection gear spacing are:
II/III - 34% [(1,9-1,25)/1,9=0,342]
III/IV - 25%
IV/V - 20%

The second one:
II/III - 31%
III/IV - 23%
IV/V - 15%

Some manuals:
Messing with a Honda Transmission
S20 Parts illustration Manual Transmission
Transmission Rebuild - 89 pics !!!

[jdmcult]

so far a d14a4 turbo drag car what is the best combiniation?

thanks