Regearing a transmission

I'm a car newbie, so don't laugh at me TOO hard...

I have no idea if this can be done (reasonably), so let me explain what I'm after.

I use my CRX SI for commuting, not racing. Today I was on the interstate at about 80 MPH, 5th gear, and my RPMs were about 4k.

At 4k, the engine is pretty loud, and it chews up a lot of fuel. Is there a way to lower the gear ratio just for 5th gear, for highway cruising? And would this save much fuel?

Thanks in advance.

Hmm, well, thats abouth right, 80MPH, at about 4 grand...... Umm, the only way to fix this, is put in a DX tranny........ You will get a loss in performance, but since your a commuter, it shouldnt matter to you.... Oh, and if you wanna get even better gas mileage, get an K&N Filter!

Would I lose performance because of the lower RPM range, or because of an inefficient transmission?

Btw, the one thing I upgraded on my car was the air filter, by RAM-FX (Are they any good)?

Originally posted by Tanked
Would I lose performance because of the lower RPM range, or because of an inefficient transmission?

Btw, the one thing I upgraded on my car was the air filter, by RAM-FX (Are they any good)?

You wont lose THAT MUCH power, its hardly noticeable.... But good things changing the the air filter, i have never heard of RAM-FX, You should just get a K&N Filter, they are great! And sound MEAN too! :)

Originally posted by MyFirst4G


You wont lose THAT MUCH power, its hardly noticeable.... But good things changing the the air filter, i have never heard of RAM-FX, You should just get a K&N Filter, they are great! And sound MEAN too! :)

Oh, its because of Lower RPM Range, not Inneficiant Transmission

I'll have to check into a DX transmission...my SI tranny is having some problems, anyway (bad bearings, says the dealership).

But there's no way to adjust the gear ratio on an existing tranny?

Thanks for the help!

Originally posted by Tanked
I'll have to check into a DX transmission...my SI tranny is having some problems, anyway (bad bearings, says the dealership).

But there's no way to adjust the gear ratio on an existing tranny?

Thanks for the help!

No prob man :)

bumpity

Originally posted by Tanked
Would I lose performance because of the lower RPM range, or because of an inefficient transmission?


you lose performance in a sense that the gears are shorter. dx tranny is ment to daily drive and commute. the si tranny has a longer final drive to compliment the faster engine set-up. it was made with the economical sports car in mind ;)

Yeh theres a way to use ur si tranny to convert into longer gears. You can put dx gears in it but i'd rather buy a whole dx tranny...less hassle.

My DX tranny is at 3500 or so at 80 mph

Wouldn't an HF tranny be a better choice? Or is it the same tranny that's in the DX?

I'll have to look into the HF tranny - I'm not sure.

But there's no practical way to say, swap out just the 5th gear on my current SI tranny and leave the rest intact? I like all of the gearing, except that 5th doesn't do much.

I don't know that much about all the gearing and everything either, but I do know that at 80 mph my DX tranny is sitting at 3500 rpm. for every 5 mph my rpm increases 250 in 5th gear. Don't know about the rest of the gears, go through them too quick, I do know that my third hits about75-80 at about 5500 rpm, engine is louder than a mo fo, but it can do 80 in third. i'm sure I'm gonna regret doing that later when my tranny blows on me. Gotta replace the bearing on mine also.

There is my little amount of info i know. hope it helps some

Originally posted by Tanked
I'll have to look into the HF tranny - I'm not sure.

But there's no practical way to say, swap out just the 5th gear on my current SI tranny and leave the rest intact? I like all of the gearing, except that 5th doesn't do much.

It can be done, but I don't know that you could do it yoruself.

You may want to ask local shops what they would charge to do it if you brought in all the parts (the tranny you wanted 5th out of).

Just a note...because of things like final drive, and tire diameter, you'll want to find a tranny that has a different 5th gear. You could end up pulling the same, or worse 5th gear than what you have if you don't do your homework.

It would be so much easyier to pull the tranny out every time you wanted different gears than to open that focker up and change the grears. BTW No a hf or dx 5th gear will not work in a si tranny cause of different spine shaft. So just get a hf tranny and call it good..

Originally posted by Cjz89civic
It would be so much easyier to pull the tranny out every time you wanted different gears than to open that focker up and change the grears. BTW No a hf or dx 5th gear will not work in a si tranny cause of different spine shaft. So just get a hf tranny and call it good..

The spines are different for different years, so some wouldn't work, but others would.

Originally posted by DRCustom


The spines are different for different years, so some wouldn't work, but others would.

ohhhhh..........

Okay heres the deal the dx, hf and si usually have the same gear ratio how ever there final gear is different (si being the biggest for better accl.). Now the dx and hf are the same. So simply changing 5th gear will do nothing but changing the final will only make your tranny a dx or hf. There is one alternative a jdm zc tranny has the smallest final gear of all the d-series trannys swapping this final into your si will give you the best top speed (down side less accl.). If i were you i would look into some mild preformance mods and the jdm zc final.

p.s. a lsd would also help but not a lot

this thread is so full of shit, i had to step in and clarify a lot of things.

the DX and Si trannies are 100% identical except for the final gear set. (yes even the bearings are the same)
the HF tranny has a totally different gearset than the DX/Si transmission and a different final drive as well.
The STD tranny is an HF tranny without 5th gear.
**the ZC tranny has its own gearset, with a DX final drive.**

the only transmission with a differnt input shaft is the 88 model transmission. this can be done away with (on an Si) by swapping in an 89-91 input shaft. (i have done this twice already with no problems whatsoever)

you can use the 88 input shaft on any engine, they all bolt up, only you will have to use the 88 model specific clutch.

**now, to answer your question...**
swap in an HF 5th gear for lower highway cruising.