I got D15b block with a Z6 head, I have the original Si tranny with 270,000 miles but don't like the short gears. I want something more suited for highway usage, is there anything out there or what can I do.

I had been told to try a ZC tranny with the Si final drive, but aren't those shorter gears that the Si tranny.

 

If you want better mileage, get a DX tranny. Performance wise, the Si tranny is the best.

 

Since you are on the highway a lot, this is what I would do in your case. Buy an Si transmission with less than 270,000 miles. Some tranny with less than 100,000 miles, if possible. Once you get that transmission, make it into a hybrid. Get a CRX Hf 5th gear. Put the 5th gear out of the Hf into the Si transmission. There you go, ideal transmission.

 

do like mach69 said, except with what you mentioned.

i'm going to start rambling about the gears in trannys, so listen if you want your question answered.

dx and si transmissions have all the same gears in them, except the final drive (or differential, you probably know, but someone else might not).

so, if you were to take an si differential and put it in a dx tranny, it'd be an si tranny.

now, zc trannys all together are slightly closer ratio than si trannys, but they use the same geared final drive as a dx tranny, so if you switch the zc final drive with an si one, you get gears that rival a jdm b16 tranny.

but, d series motors don't rev as high as a b16, so you might want a different 5th gear in there, that's when the hf 5th gear comes in, because of the different final drive, it won't be as tall of a gear as in the hf tranny, but it still will be a nice low rpm cruising gear.

 

What are you going to do with your Si tanny? Because i've been looking for one for awhile.

 

I don't know yet I mean when you shift around 7k it grinds, I am actually thinking about converting to a hydro tranny and getting a CX tranny depends on the cost though

 

if i were you, i'd just take it apart and replace the synchros rather than converting it to hydro clutch. those newer trannys aren't really that great, they have problems too. the task sounds hard to take it apart, but it's actually really easy to do on these trannys. there's even a bunch of how-to's online.

i know you *might* be able to get a good si tranny for cheaper than a set of new synchros, but this way you know that they're new, you don't know anything about the "tranny you got from this kid who said it was good"

 

so where is a good place to buy new gears for a rebuild?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by subydoored &raquo;</TD></TR><TR><TD CLASS="quote">so where is a good place to buy new gears for a rebuild?</TD></TR></TABLE>

http://www.gear-speed.com

 

My mini-me with a zc 1-4, si 5th and final drive got 37mpg doing 80mph with the A/C on.

 

check out effin motorworks