new final drive gear in honda civic?
 

Is there a way—without replacing an entire transmission—to swap a final drive gear in a honda civic?

This may highlight my limited understanding of how these things work.

My transmission is in great shape and probably will be for the forseeable future. It seems like something of a waste to pull the whole thing off just to change the final gear ratio.

My civic is a 97 civic dx hatchback and has the same final drive gear as the hx civic. I'd need to go to the older cx/vx to get something used that would get me a taller gear. Can I buy something new?

So you want to pull your tranny, take it apart and put some brand new parts in because it's going to be easier and cheaper then going to a junk yard and buying a complete low mile tranny for $100-200 and just installing it, then either selling your current good tranny for close to that same amount or at least getting your core deposit back.
Even the Honda dealer manual doesn't really tell you how to take appart the tranny, they pretty much tell you to let the guy who does that use the transmission manual, tools and calibration equipment do that.

You make an excellent point.

I'll start sniffing around for an appropriate transmission.

Final drive on Civic auto trans
 

Looking over the 96-98 Honda service manual, I noticed that the final drive 4th gear on the automatic transmission is taller than the 5th on the manual. On the auto it is 0.638 and on the manual it is 0.702. That's a pretty big difference. I think it is better than the 98 HX. Is there any reason to think it could not be swapped (I know it's not regarded as totally practical). I'd just like to know, in case someone drops one in my beggars cup one day I want to know if I can use it. :confused:

changing the 5th gear depends a lot on if it will "mate" up to the final drive gear.
if it wont, then it isnt something to even consider.
as far as if it will, I havent a clue.

The final drive gear is the ring and pinion. None of the gears mate with that, so that isn't a concern.

The two shafts that the gears ride on may be different (different diameter, different splines) and that would mean you could not swap. I don't know if they are or not. I do know that you can swap the 5th gear around between D-series transmissions. The 2nd-gen CRX HF will have the tallest 5th gear, though I have read that it isn't a whole lot taller than the 5th from the later Civics. (Something like 0.704 to 0.712 ratio?)

The shop manual for my CRX talked about disassembling and reassembling the transmission. I also used a how-to article from the crxcommunity.com website when I took mine apart and put it back together again. (The input shaft bearing on these seems to die if you leave the oil level low for a long while.)

There is a guy called "Mista Bone" who hangs out on the CRX Community board and more than likely other boards that talk about Civics. He seems to be the D-series transmission guru, although he has some fairly backwards ideas about what makes for good fuel economy...

If your Civic has a B-series engine, I have no idea what will interchange.

-soD

that is essentially what I meant :)

What kind of driving do you normally do? If it's below 55 or so the gears should be fine.

Oh. I checked your fuel log and it says "highway" a lot. In that case the swap would help a fair bit.

Thanks guys for your responses. Intriguing to think a 2cd generation 2nd-gen CRX HF 5th gear could fit into my D series sixth gen transmission. Here's another related question, this time about the final gear ratio. My 2 door coupe has 4.034 listed as the final reduction, whereas sixth gen (96-98) Hatchback is listed as 3.722. That's better, no? Why don't more modders talk about swapping that? Bigger pain than its worth relative to the transmission swaps?
EDIT: both the hatch my coupe have the D16Y7 engine.

a full trans swap is by far easier.
if both engines are the same, the chances are very high its a straight bolt up.

What they said. If you really want to build a transmission, go over to d-series.org and read up on the transmission build threads. They are typically building for high power and shorter gearing, but the same skills would apply. You can do it yourself if you'd like. Get ready to spend some quality time, though.

I talked to a guy in north carolina recently who was selling his 5th gear. I was interested in doing something similar to what your talking. He explained after swapping in the 5th gear from a hf into his crx dx the results weren't even close to his expectations he said it only lowered his rpms @ 60mph by about 200rpms. I wish I could remeber his explanation clearly but I can't. Bottom line from someone who did it. swap the entire trans. I have since purchased a hf trans for my 87 crx si.