how hard is it and could I do it myself??? and will a 88 hf tranny and a 90 si tranny mate up for that reason

 

i thought the HF was a 4spd.

 

its only as hard as opening up the transmission. kinda tricky if you havent done it before. get a snap ring plier. and you want to have a clear description of each part so you dont reassemble things wrong, so a helms manual is a must. 5th gear is on top, so you dont have to take the whole assembly apart. but i bet you would anyway since youre in there. i would anyway.

HF's were not 4 spd. only the civic STD was 4 speed.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by donaldmejr &raquo;</TD></TR><TR><TD CLASS="quote">how hard is it and could I do it myself??? and will a 88 hf tranny and a 90 si tranny mate up for that reason</TD></TR></TABLE>

I am thinking about doing the exact same thing.

 

The only 4-spd was the STD hatch, no crx came 4-spd (unless if they were automatic?)

You will notice a slight difference in rpm. At 80 on my Si transmission I am around ~4100 rpm. I have heard that you would be at like ~3500rpm with the hf 5th.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mach69 &raquo;</TD></TR><TR><TD CLASS="quote">The only 4-spd was the STD hatch, no crx came 4-spd (unless if they were automatic?)

You will notice a slight difference in rpm. At 80 on my Si transmission I am around ~4100 rpm. I have heard that you would be at like ~3500rpm with the hf 5th. </TD></TR></TABLE>

I had an HF tranny on my D15B2 and 80 mph was like 3100 RPM.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FOMULA91 &raquo;</TD></TR><TR><TD CLASS="quote">

I had an HF tranny on my D15B2 and 80 mph was like 3100 RPM. </TD></TR></TABLE>

Thats great and all, but the final drive on the Si transmission is different from that of the Hf transmission.

 

what do you mean its "different" does that mean it wont work??? I was figuring that b/c the hf is a 88 with 21 splines and the si is an 90 with 20 splines then it would cuase some problems. By the way my hf runs at 2500 rpms doing 80 mph and 3100 rpms doing 95 mph

 

I thought the final drives were the only thing that changed, maybe Mistabone can chime in on this topic and clear it up? i was thinking of getting the ATS aftermarket final drive and putting an hf 5th aswell. ....hmmm bump for more info

 

http://home.cinci.rr.com/mistab0ne/tranny.html

There. If you want a cx fifth gear I can get you one, .

 

HF 5th gear in Si transmission will result in very slight difference in rpm in 5th from stock DX transmision

Si with HF 5th = 4.25 x 0.694 = 2.9495
Stock DX 5th = 3.88 x 0.771 = 2.9915

 

He doesn't have a dx tranmission, so I don't understand the comparison.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jlicrx &raquo;</TD></TR><TR><TD CLASS="quote">HF 5th gear in Si transmission will result in very slight difference in rpm in 5th from stock DX transmision

Si with HF 5th = 4.25 x 0.694 = 2.9495
Stock DX 5th = 3.88 x 0.771 = 2.9915</TD></TR></TABLE>

I have a dx, and an si transmission. I can get an hf 5th gear. For lots of highway traveling is the the hf 5th gear worth it?

 

Don't waste your time / energy / money.

My SI/ZC hybrid tranny (for the short gears, not long highway gears) got 37MPG with the AC on @ 80MPH.

If your MPG sucks that bad.. you have bigger problems than gearing.

 

Yeah, I see what you are saying.