Quote:
Originally Posted by Ecky
Honda transmission gurus, I have a question.
At some point I might be interested in making Aerocivic's gearing even taller. Looking at the charts, the 88-91 HF has the tallest ratios possible, and would result in a 10.3% reduction in RPM in 5th gear. 1.2% of this is from 5th gear being slightly taller, and the other 9% is from the final drive.
The notes say that the countershaft is shorter for the 88-91 CRX than in 92-00 Civics, and the countershaft is part of the final drive (FD is the ratio of the countershaft and ring gear on the diff). This suggests to me that I cannot swap the final drive from the CRX HF into the Civic gearbox, and the 5th gear alone would be virtually meaningless.
Meaning, if I want the HF gears in Aerocivic, I probably need to put in the complete HF gearbox.
Where this is difficult:
-The differential might not be in the same spot, meaning the axles may not be the right length anymore.
-The transmission mount will be different. I can fabricate this though.
-The shift linkages might not bolt up / work
-The bits that mount on top of the transmission (e.g. airbox) likely will not have anything to bolt onto
-Cable to hydro conversion would be required at the transmission
-VSS will need correction. Hopefully it's electrically the same.
Anyone have details on any of these points for me?
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The HF box is really tall. I loved it in my Civic Wagon. I think 60 MPH was 1800 RPM. I usually cruised at around 1200 RPM. At higher speeds, I still wanted even taller gearing! My one complaint is that it has a similarly weird 1-2 gear spacing as the Insight. Big RPM drop into 2nd gear. I'd prefer the regular Civic 2nd, 3rd, and 4th with the HF 5th and final.
Does the 5G Civic have a VSS? The HF box has a mechanical speedo cable.
The input splines are something to keep in mind when sourcing the HF box. The 89-91 box is probably easier to use. From what I've read, the '88 box can be used, but might require mixing and matching clutch parts.
88 = 21 splines
89-91 = 20 splines
