If it's something that I can't fix myself would if be better just to get the ZC transmission?
Whats the difference between ZC and the SI, is one better than the other?

From a performance standpoint which is better as well.
From a daily driver standpoint as well.

 

Here you go http://hybrid.honda-perf.org/tech/zcsifdswap.html

 

what does that have to do with his problem?

 

I mean that site makes sense but doesn't correlate to what I'm asking. Unless I'm just stupid this morning.

Okay I'll go into my problem even though this is supposed to be more on the si vs. zc.

My 5th synchro I believe isn't working. Just woke up and drove for a while and it would NOT go into 5th gear. SI Tranny on ZC engine.

I cannot find an SI tranny for sale nor a ZC tranny... YET. I am still wondering if I should try to rebuild it but I know NOTHING of rebuilding transmissions yet. I've swapped my engine and all that jazz so I figure its about the same process

Step 1: Take it slow.


haha.



But ya, back to the topic. Whats the difference performance, either numbers or real time feel of how each other feel.

 

I can't confirm off the top of my head which is better than the other (plus that's more personal taste than anything else) but if you play with a gearspeed calculator using their respective gear ratios you might see what I'm talking about. The DOHC ZC tranny has the same final drive as the DX tranny does. This means that from a mechanical standpoint the only thing that is different is the individual gear ratios themselves which are closer relatively speaking. The DX and the Si transmissions actually share the same gearing with the only difference mechanically being the final drive. What I just said may or may not make any sense but it's hard to say one is a definitive better transmission. What I can say is that from personal experience, the DOHC ZC specific gears actually put you up higher in the next gear vs Si/DX gearing. If that sounds good, the ZC is the way to go. If you don't like the lower final drive, switch to an Si final drive. I hope someone can chime in and better explain it.

Also, although there seems to be some debate about it, if you run the DOHC ZC tranny you'll need the matching halfshaft.

PS If you need help, I'd be down to drive up and help you out. Also, my car has the gearing posted up there (ZC 1st-4th, Si 5th and final drive). You can drive it, if you like it then do the same. If you don't, fix yours or buy another tranny. I have a box full of spare parts too, probably got what you need to fix yours.

 

Axles will be an issue with the ZC. As stated, you'll want the half shaft. Or you can swap out the differential carrier. Rebuilding the transmissions are easy - if you have the right tools. I have over $250 invested in transmission tools, and still need to invest more (you can never have enough tools, right?) to be able to do everything without borrowing tools.

 

I assume you're asking about the 88-91 dohc zc tranny comparison. "ZC" isn't very specific.

2-5 gearing is different and so is the final drive compared to the Si. With the 3.88 of the DOHC ZC tranny (same as DX) the higher gearing in the 2-5 gears is a wash compared to the 4.25 of the si fd. You can do your own hybrid gear swaps, whatever combination you want if ur inclined.

The DOHC ZC tranny requires the CORRECT half shaft (must be manual, must be D series, not the same as wagon), and then the right length axles (DA will do).

So if you don't have the axles or half shaft, you're already looking at a more expensive tranny.

If you can't get it into 5(h, then its not your sycnhros. Its probably a bad fork and the tranny is toast inside. Best to find a local DX or Si tranny and swap, or rebuild the old one with good condition parts. Parts are swappable with DX trannies. Its just the final drive and carrier bearings that are different.

 

Alright well it looks like right now I'm currently heading towards the idea of REBUILDING my current (SI) tranny. I think it'll be more cost effective.

Anyone think they got a couple ideas of what it could be causing my current problem? As posted above I'm not a transmission type of guy.

It won't shift in 5th. Feels as if there's a wall stopping it. I can't get it into the general area of 5th but if I try to put it in 5th and let go of clutch+gas it, all that happens is it revs high while I decelerate.




Vehicle: DX 90 Hatch
Engine: ZC
Tranny: SI 5 Speed

 

just get a dx trans & put the si final drive. Or get a 4.5 fd from synchrotech. Thats what im doing to my dx since its the same 1-5 gears.

 

Wasn't there a "Hybrid ZC trans" that people were building? I don't remember exactly what it was, but it was something like an Si trans with ZC 4th & 5th gear.

 

 

Check fluid, you likely ran it low and the 5th sleeve assembly is now burned up.

Gearing wise the ZC (if DOHC ZC) is better. Gears are closer though the FD is longer. Ease of use is the Si as you just use the Si axles.

 

Is it possible, since I have an old Si transmission and a ZC, to put the guts of the ZC into the Si case? Mainly to get around the axle dilemma.

 

Yes, there's two ways to go about it.

1) swap the entire main and counter shaft with their gears intact along with the ZC diff gear. This will essentially be a ZC geared Si transmission.

2) swap the ZC main shaft with gears over to the Si transmission and transfer the ZC countershaft gears onto the Si countershaft. This will result in the ZC gearing combined with the closer final drive set from the Si transmission.

In addition you can use the Si 5th in combination with the ZC 1st-4th fears to slightly lower the freeway RPMs.

 

Thanks! Really appreciate it!

 

You guys are misinformed. The ZC tranny that is different is out of a Rover which is why its different and so hard to come by. Yes the halfshaft is different as are the gear ratios but unless you know someone in the U.K. who can get you one, its highly unlikely that you'll ever come across one. The japanese one is the same an SI tranny. If it wasn't there would be a plethora of them floating around from all of the ZCs that were imported over the years.

 

incorrect.

and its a little scary that you seem so convinced by such wrong information....

 

I have no idea why you want more headaches with the ZC transmission. It might have more benefits, but good luck getting axles for it.