which tranny is better for a DOHC ZC motor...a ZC tranny or a Si tranny. ive heard that the Si tranny has closer gears, but i dont know if thats true..so i was wondering which to buy for my ZC swap. thanks.

matt

 

si

 

Si tranny with with ZC Differential or ZC tranny with Si final drive. The half shaft of the ZC tranny is nice.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">Si tranny with with ZC Differential or ZC tranny with Si final drive. The half shaft of the ZC tranny is nice.</TD></TR></TABLE>

Si tranny + ZC Diff = DX tranny with an intermediate shaft, unless you go to the trouble of swapping the Si final drive ring gear onto the ZC diff unit. If you do that, the only thing you gain is the intermediate shaft.

The ZC tranny has closer-spaced gear ratios, but has the same final drive ratio as the DX tranny. The Si and DX transmissions have the exact same 1-5 gear ratios, but the Si has a more aggressive final drive ratio (4.250 for the Si, and I think 3.880 for the DX and ZC, except for the '88, which got something like a 3.79 or some such).

Stock for stock, a ZC transmission and an Si transmission perform pretty close to one another. The big differences are to be found when you "hybridize" your transmission: ZC gearing (some simply use the ZC 1-4, others just use the ZC 3-4) with Si final and diff. The upside is that you get the better final drive ratio, AND the closer-ratio gearing, AND you get to keep using off-the-shelf Si/DX axles. The downside is that you don't get to use the intermediate shaft (which typically doesn't come with the transmission anyway, and you get charged extra if you want it), so you'll notice a little bit of torque-steer under hard acceleration in first and second.

On my '91 CRX DX, I went with the ZC 1-4, and HF 5th gear, and the Si final/diff unit. I used the HF 5th for a couple reasons: (1) We wanted to see if it would work, and if so, how well; and (2) I liked the idea of a more relaxed highway cruise. Instead of seeing 4000rpm @ 80mph in 5th, like the stock Si would give me, I now see about 3500@80mph. And highway mileage goes way up (averaged about 43mpg on a long trip with two 250-lb guys, a bunch of luggage, and a spare transmission that we were taking from Georgia to Texas. A/C was on the whole way.)

Now we're working on a "Super-Hybrid" for one of our upcoming project cars: 4.43 FD, LSD, and ZC gearing, with an intermediate shaft. Should be fun, especially when it gets bolted to a high-compression D-series in a lightweight '88 CRX HF.

If I had to choose between the Si or the ZC transmission, and I was just putting a stock tranny in the car, and I already had the Si or had to buy the ZC, I'd go with the Si. It's cheaper and easier in most cases, and if you're not going hybrid with the tranny, it probably makes more sense. And it seems like ZC transmissions are getting harder to find, and the price is going up.

Mike

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Kwicko &raquo;</TD></TR><TR><TD CLASS="quote">"Super-Hybrid" for one of our upcoming project cars: 4.43 FD, LSD, and ZC gearing, with an intermediate shaft.</TD></TR></TABLE>

i think you need to let me test that out for you guys...

 

Yeah, we're still pulling all the parts together for that one... And trying to decide what gearing will actually suit the car best. We're leaning towards building the engine more for high-rpm HP, but if we can find any torque in it (I know, "torque" isn't exactly something that goes with "D-series"...), we might find the ZC gearing with that 4.43 FD a little TOO close. It's being built up for an autocross-only car, so streetability isn't our highest priority. If it all comes together the way we want it to, it'll be damn near like shifting a sportbike - WAAAAA-WAAAA-WAAAA-WAAAA - "Oh SHIIIIIITTTTT!".

We autocrossed David Strawn's (davens) '89 CRX with a B18B and a close-ratio LSD-equipped transmission in it for a few events. Where we were normally in second gear in any other car, I had his well into third gear, pulling it up to 5500rpm in third! Maybe this new beast will have us shifting into fourth gear on the autocross course!

 

Keep us updated on these trannys
BTW its nice to see you "over here" you got alot of info thats worth sharing.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Kwicko &raquo;</TD></TR><TR><TD CLASS="quote">
And it seems like ZC transmissions are getting harder to find, and the price is going up.
</TD></TR></TABLE>

I thought that was the opposite, if you check out ebay or hmotors they almost always have a ZC tranny up for sale. I got my ZC tranny with my engine last month for an extra 100 dollars. Hmotors just reently dropped the price on their ZC tranny's by 50 dollars.

 

what are the top speeds of the zc and si? i heard the zc has a closer 5th gear so some dont like highway driving but how much of a difference does that make?

 

the zc tranny is lower geard. but highway, 55 mph is like 3500 rpms. swap out an si final drive into the zc and you have a good trannie. it is also stronger. i had one in my crx si with stock engine. i have 86 accord axle shafts on my crx axles and a 86 accord clutch with crx pressure plate. everything seemed to work good

 

Kwicko, I am so looking forward to my new EffinMotorworks hybrid tranny on the 22nd. Are you going to be there?

 

Dewarcr: Yup, I'll be there. Who the hell else is gonna do all the wrenching? Just kidding - David and Reuben should be there as well.

As for top speeds... Well, the CRX Si is "officially" listed as having a top speed of 120mph in all the magazine tests I've found. A ZC shouldn't be that much different. A ZC with Si final is supposed to have a top speed around 112mph, though (@6500rpm in 5th gear).

Mike

 

zc tranny si final drive queefe lsd

 

Kwicko, with the HF 5th gear, are you able to top it out any higher? I want to do a build similar to yours but maybe just throw the HF 5th into my Si trans. Obviously theres no need to drive that fast, but thats not what this is about.

 

when did the hf become a 5 speed rather then a 4 speed?


and anyone use a phantom grip lsd in an si tranny?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pSI civic &raquo;</TD></TR><TR><TD CLASS="quote">when did the hf become a 5 speed rather then a 4 speed?


and anyone use a phantom grip lsd in an si tranny?</TD></TR></TABLE>

I'm also wonderin about the Phantom grip. From what I've read so far ppl seem to say Quaife &gt; OBX&gt; Phantom grip. Phantom is also the cheapest i believe. Input?

Edit: i dont remember if its 4 or 5, coulda sworn it was 5speed. but yea, i want that gear! lol


Modified by 89SiPimpin at 12:01 AM 1/10/2005

 

[QUOTE=pSI civic]when did the hf become a 5 speed rather then a 4 speed [QUOTE]

the hf tranny has always been a 5 speed. it's the civic std tranny that's a 4 speed.

 

i thought the hf and std were the same thing. or is that a difference between the crx and hatch?

 

std is DX with 4speed trans pretty much, also has dpfi. HF is 5speed and has mpfi

 

well then why was i looking at a crx hf with a 4 speed and dpfi... and why is the 4 speed tranny comonly refered to as the hf tranny?

 

i am pretty sure it was an hf crx.

 

I love my ZC tranny

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pSI civic &raquo;</TD></TR><TR><TD CLASS="quote">well then why was i looking at a crx hf with a 4 speed and dpfi... and why is the 4 speed tranny comonly refered to as the hf tranny?</TD></TR></TABLE>

i personally have never heard the 4 speed tranny referred to as an hf tranny. i've always heard the 4 speed tranny referred to as the std tranny. now i could be wrong but i believe that the std was the only one to come with the 4 speed. now as far as a crx hf having one, that could simply be that someone blew their hf transmission, and just got the 4 speed as a replacement. why? maybe it was the only one they could find at the time and just really needed a tranny.

 

i am pretty sure that the hf is a 4 speed... i think i may be wrong about the type of fuel injection though. i am pretty sure that the std/hf tranny is the same.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pSI civic &raquo;</TD></TR><TR><TD CLASS="quote">i am pretty sure that the hf is a 4 speed... i think i may be wrong about the type of fuel injection though. i am pretty sure that the std/hf tranny is the same.</TD></TR></TABLE>

i've owned 2 hf's and both had a 5 speed tranny. they are famous for having the really long gears. can hit like 70mph in 2nd gear. granted it take forever to get there but they do come with 5 speeds.