Is it possible to put an HF of VX 5th gear in an Si tranny for reasons of better gas mileage?

 

yes you can put in an hf 5th gear in an si tranny for gas milage. it will also give you a higher top speed.

 

hf 5th will fit in.

 

How about a LX/HF tranny with a Si Final Drive Thats What Im Gonna Do

 

sweet. i think ill put that on my to-do list. right behind exhaust, tires, puttin on the rear discs, and paint

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHCKLR657 &raquo;</TD></TR><TR><TD CLASS="quote">How about a LX/HF tranny with a Si Final Drive Thats What Im Gonna Do </TD></TR></TABLE>

pretty much the same thing i think.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHCKLR657 &raquo;</TD></TR><TR><TD CLASS="quote">How about a LX/HF tranny with a Si Final Drive Thats What Im Gonna Do </TD></TR></TABLE>

btw, the LX (4dr sedan) has a 4.0 final drive (actually all 4dr sedans do), as opposed to the 3.88 3dr/CRX DX and the 4.25 Si.

thought id mention that.

sounds like you might just want to find a Si box and stick a HF 5th gear in it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tyson &raquo;</TD></TR><TR><TD CLASS="quote">the LX (4dr sedan) has a 4.0 final drive (actually all 4dr sedans do), as opposed to the 3.88 3dr/CRX DX and the 4.25 Si. </TD></TR></TABLE>

really? wow, its been a long time since i could say "huh, ya learn something new everyday..."

 

yah, felt the same way when i first learned that too. i confirmed with the civic helms manual.

 

so its all sedans? even the DX?

 

yep. all years. all sedan models 88-91, even EX.

btw, 88 DX crx had a lower than 3.88 FD too. i think 3.72. not as low as HF tho. i credit that one to bone for pointing it out.

 

thats good to know.

 

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

really? wow, its been a long time since i could say "huh, ya learn something new everyday..."</TD></TR></TABLE>

 

i think it would be an interesting setup being so streetable. do many people do that type of gear swap in d series? i have heard about it in b series. how difficult would it be?

 

there is a guy one here, i think his name is quicko or something like that. he's done the hf 5th gear into si swap. ask him about it.

 

thanks. hybrid trannys are cool

 

soo...im confused. I was told a while ago that you cant just change the 5th gear on an si tranny to rev lower as it has to do with the final drive ratio of the tranny....Can someone please explain?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pSI civic &raquo;</TD></TR><TR><TD CLASS="quote">yes you can put in an hf 5th gear in an si tranny for gas milage. it will also give you a higher top speed.</TD></TR></TABLE>

Well... theoretically, at least. The Si final drive/HF 5th combo *should* be good for a top speed of around 148mph at 6500rpm, if memory serves. I say "theoretically" because it's going to be tough to pull enough power out of a D-series (without forced induction, at least) to actually push it through the air that fast.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pSI civic &raquo;</TD></TR><TR><TD CLASS="quote">there is a guy one here, i think his name is quicko or something like that. he's done the hf 5th gear into si swap. ask him about it.</TD></TR></TABLE>

Yup, that would be me. I'm running a hybrid D-series (L3) transmission with ZC 1-4 gears, HF 5th gear set, and Si final drive, all bolted to a D16a6 (Si) engine and dropped into my '91 CRX DX. That's it for mods on the car, and it's noticeably quicker with the A/C *on* than my '90 CRX Si is without any A/C.

People talk a lot about the RPM dropoff when shifting from 4th to 5th, and it *is* there, and more noticeable than the straight Si's rev drop, but it's not bad. The way I see it, if I'm running the car up near redline in 4th and *still* need more acceleration going into 5th, I'm pretty well screwed already. Can't outrun police radio! Highway gas mileage is great; around town mileage suffered a little, but I have to absolutely flog the thing around town to get less than 33mpg out of it. On long highway trips, it usually pulls 42-46mpg with the A/C on and cruising at around 80mph.

If I had it all to do over again, I would, definitely. Absolutely no regrets here.

Mike

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mattie_96 &raquo;</TD></TR><TR><TD CLASS="quote">soo...im confused. I was told a while ago that you cant just change the 5th gear on an si tranny to rev lower as it has to do with the final drive ratio of the tranny....Can someone please explain?</TD></TR></TABLE>

well, final drive DOES NOT mean 5th gear. changing the final drive affects ALL the gear ratios. and 5th gear can be interchanged independently. not sure if you knew that.

 

ok the only difference between the si/ex tranny and dx/lx tranny's is the final drive gear, on the differential. I am not familiar with the hf gears themselves, but I know the final drive is super low.

lets say the hf gears are all lower, then you could put a 5th gear from that into either of the others, but if you want a better setup, you would want to have the si final drive gear.

anyone more confused? good.

 

88-91 HF 3.250 1.650 1.033 0.823 0.694 FD 2.954
88-91 DX/EX/LX 3.250 1.894 1.259 0.937 0.771 FD 3.880 (4.0?)
88-91 Si 3.250 1.894 1.259 0.937 0.771 FD 4.25

 

so how hard is it to do the swap?? anybody know any body on here that will do it? anyone have a GSR tranny with an lsd and a hf or ls 5th gear??

 

hahaha. I put the Hf l3 tranny on my 87 4dr. I get about 48mpg now. hahahahaha...suckas i made me own crx hf. hahahahaha...I love it. I can barely get on the freeway but i'm beating everybody at the pumps. I drove about 550mi on one tank. Gotta love those tall gears.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by reed857 &raquo;</TD></TR><TR><TD CLASS="quote">so how hard is it to do the swap?? anybody know any body on here that will do it? anyone have a GSR tranny with an lsd and a hf or ls 5th gear??</TD></TR></TABLE>

D and B series gears are not compatible. So, you'll have to use the LS 5th, and yes, it's been done/discussed more than once.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Burlyirishdude &raquo;</TD></TR><TR><TD CLASS="quote">hahaha. I put the Hf l3 tranny on my 87 4dr. I get about 48mpg now. hahahahaha...suckas i made me own crx hf. hahahahaha...I love it. I can barely get on the freeway but i'm beating everybody at the pumps. I drove about 550mi on one tank. Gotta love those tall gears. </TD></TR></TABLE>

Wow man, I got a kick out of that one. Thats crazy, 550 MI ON ONE TANK!!
Jeez man. I think I'm going to have to get a daily beater and do that.