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Old 01-23-2008, 09:38 PM   #1 (permalink)
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Standard trans swap for '96-'00 Civic?

For '96 - '00 Civic - Can one swap in a different tranny or some different gears?? I'm only talking about standard trans here, not auto. Maybe just a final drive swap for lower rpms?

For me I think that taller gearing in top gear would be the goal. I'm on the highway a lot. Of course I don't want to be crippled in town but a slightly higher 1st gear plus slightly taller spacing between all steps should give a good drop in rpms when in 4th and 5th, right? Or any path to a higher 5th gear might be good of course.

I gotta admit, not (yet) owning any Honda I'm not familiar with the different trannies etc. that were used. So I hope you'll be gentle and not send my head spinning with toooo much new jargon.

I find not too many HX on the market. But plenty of the other versions like EX, LX, DX. If one could change the gearing you could probably get a few extra mpg... probably nearly as good as the HX mpg when you're all done. Just without the lean burn - but we know it's possible to get good FE without lean burn. And cheaper Oxy sensors, too!

My mechanical skills are medium. I've been pretty intrepid in modding my own car and have done my share of tuneups, brake work, some suspension work - but I've never pulled an engine or tranny and never pulled a head.

Comments?

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Old 01-23-2008, 09:45 PM   #2 (permalink)
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Your best bet would by the transmission from a 92-95 Civic CX or VX,

The swap isn't too hard. Mehbe a day if you're motivated (for a first timer).
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Old 12-17-2010, 11:35 AM   #3 (permalink)
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Looks like I am going to try to resurrect an old thread- this is exactly what I am thinking of doing as well, I hate driving down the freeway at 3100RPM... and my family will not put up with me not doing the speed limit... my wife's POJ Hyundai Elantra gets better MPG at 70 than my civic, and that's just wrong

Could you really just drop a CX or VX tranny in the civic? how smart is that for longevity? My civic only has 125K right now, and has never been changed from stock. although I plan on keeping it forever.

What about that elusive gear swap for 5th gear? that seems smart to be able to leave everything the same except for the 5th gear. Do you have to take the whole tyranny out, or can you get in there to swap them? another thought, I can easily skip 4th when accelerating, what about moving the 5th gear to the 4th gear and adding an even taller '6th gear' in the 5th position? Does anyone know all the details on this kind of thing?
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Old 12-17-2010, 02:16 PM   #4 (permalink)
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It looks like all of the Civic models sold in the US (except for the Si) in 96-00 used D-series engines. They probably had hydraulic-actuated clutches, rather than the older cable-operated style. So any hydro trans from a Civic with a D-series engine should work. Also, any gear sets from one of those Civics should work. So the rare and elusive 88-91 CRX HF 5th gear will fit and will work. But I am told that the later transmissions have a 5th gear that is almost as tall, so it may not help much?

Changing the final drive may be more cost than you might want. I'm not sure how precise the tolerances are in the Honda transmissions, but I know that in some other older ones you keep the ring and pinion with the transmission case because the tolerances get out of whack if you don't.

I would be tempted to look into taller wheels and tires to drop the RPM on the freeway. Unfortunately, the speedometer will read lower than your actual speed after you do that, but it is a lot easier than a transmission swap or re-gearing your existing trans.

-soD
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Old 12-17-2010, 03:08 PM   #5 (permalink)
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Yes, I have looked at the tires too, but you can't realistically get a 10% gearing difference... and if you did, the car sure would feel sluggish in the lower gears... and turning would become hard to do.

If I was able to swap the 5th gear in a 98 civic with a 88-91 CRX gear I would lower cruising RPM's by 9.8% almost 300 RPM at 65mph

.702 ratio to .771

Is it really possible? I really have no idea what is inside the transmission, or if the gears are compatible or not. And the issues you mention with tolerances kinda scare me...

What about the new civic, it looks like the 5th gear of a 2002 EX has a ratio of .757, so a 7.3% improvement- would that gear fit in a 98 civic tyranny? That surely would be an easier gear to find...
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Old 12-17-2010, 03:16 PM   #6 (permalink)
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shoot I've been doing all my math wrong haven't I... I have it reversed, I really want the gear ratio to be lower right?

that leaves the only tranny that was for the CRX HX in the 88-91 years... that one was .694- only a 1.1% advantage- was I doing my math wrong?
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Old 12-17-2010, 10:16 PM   #7 (permalink)
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Right, it's the second: Lower numbers are taller gears.

If the performance would be sluggish with the larger tires, it would be nearly as sluggish with a taller final drive (ring and pinion).

I don't know if the later Civics used D-series engines or not. (Some of the Si models used B-series engines/transmissions.) You can swap gears among the D-series transmissions, but not with B- or K-series ones.

The CRX HF also had a taller ring and pinion set, so together with the taller individual gears you had very tall overall gearing indeed. It may be possible to swap the R&P over, but I'm not sure. That will effectively make all of the gears taller. But I don't know the exact specs of either the one you have now or the HF one...

-soD

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