Before you flame me I did search the archives and even after reading through at least a half dozen posts and after talking to various people who either race SCCA or HC I've still got 10 different answers and am even more confused.

Here is the situation:

I race an Integra with an LS gearbox. 5th gear as you all know is useless on this car. I want to either add a 4.7 or 4.9 final drive. I know it will make the car accelerate quicker in the first four gears but my confusion stems over 5th gear.

The question is simple, but no two answers I have gotten are the same. Will the car pull better in 5th gear with the new final drive? Some say yes, some say no, some say it depends.

Example, at Summit Point Raceway with a stock gearbox I have to shift halfway down the 3000 ft main straight into 5th. Shifting from 4th gear at 7100 rpm's and roughly 115 mph the motor drops to 5000 rpms and bogs down. I gain maybe 2-3 mph.

I did some calculations on a website and with 22.8 diameter tires, stock LS 5th gear and a 4.9 drive I would have to shift into 5th gear at about 101 mph which would mean I would be in 5th gear down the entire front straight at Summit.

Would the car pull better and gain more speed in 5th with the 4.9 then the 4.2. Some have said that the 4.9 will drop me back to 5000 rpm's when I hit 5th gear same as with the 4.2. Other's say I will be at a higher rpm and the car will pull harder.

I know the car would be quicker everywhere else on the track and in all the first 4 gears but if the motor is going to bog down in 5th at 5000 rpm down the whole straight I am hosed.

If this seems like a really simple questions, please excuse me as I am a mirror image of "Cole Trickle" in the 80's NASCAR movie "Days of Thunder" where Tom Cruise admits he doesn't understand a damn thing is crew is talking about (technical stuff) he just drives the damn thing.

Advice, info, opinions appreciated.

Regards,

Jon P. Kofod

 

since you asked for opinions as well as useful, knowledgeable advice, let me give you my opinion (and god knows I've been known to be wrong often... )

You should drop back to the same RPM from one gear to the next, regardless of final drive (the spacing is still the same from onw gear to the next, right?)
So yeah, you'll end up at 101pmh and 5000rpm, instead of 115pmh and 5000rpm.
but you should have more effective torque to the wheels thanks to the shorter final drive. And that should help you pull harder. But up to what speed? Yo no se, senior. Sorry.

 

Well that would back up what my mechanic told me when he said "...you'll drop back to the same rpm but you'll be going faster..." which confused the heck out of me.

Regards,

Jon

 

Jon - I've gearing spreadsheet I can email you if you want.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FLATOUTRACING &raquo;</TD></TR><TR><TD CLASS="quote">Well that would back up what my mechanic told me when he said "...you'll drop back to the same rpm but you'll be going faster..."
</TD></TR></TABLE>

Actually, wouldn't it be: you'll drop back to the same rpm but you'll be going slower?

My stance is that the RPM's when you shift into 5th will be the same regardless of final drive. Your problem is that the LS 5th gear is just too tall...

You should be able to accelerate slightly better in 5th at 5000rpm with the 4.9 than the 4.2 - but I'm not sure if it'll be enough to get you to your powerband (wherever that may be).

 

Run the highest FD you can put in the car without running out of gear at the fastest track you visit. In other words, if the fastest you ever see is 125mph and the 4.9 allows you to go to 130mph, run the 4.9.

Otherwise, go low enough that you hardly ever use 5th gear. I had the 4.7 in my GSR and 5th was still a dog. Exiting hog pen I'd run up Shultz's *** until I had to catch 5th gear, then he'd pull away (he had the stock 4.4) because he was still in 4th gear. By the time he went to 5th he was on the downhill part of the straight.

Try to custom fit the FD to the tracks you run most. You may find that the stock unit is the way to go.

 

Scott,

You example is exactly the one I am concerned about. At Summit it makes no difference if I stay in 4th or shift into 5th half way down the straight. In most cases I still end up with a top speed of 117 -119 at the end of the straight.

I am worried that I will have the same problem at Summit that you have at Hog Pen. The question is will I pick up more speed and quciker lap times elsewhere.

The two tracks I spend the most time at are VIR and Summit Point and in both cases I only need 5th gear on the straights. At Summit I can stretch it out to past half way or stay in 4th and at VIR about the same.

So it appears that I would have to spend much more time in 5th at both places and give up time on the straights.

When you installed the 4.7 (assuming you had a stock FD in it the car prior) how much more pull in 5th, if any, did you notice?

RJ,

Thanks! I used the one at http://www.autocrossing.com/cgi-bin/gearcalc.cgi which seems fairly accurate.

Decisions, decisions....................

 

If you spend a lot of time at VIR (and I don't know squat about SP), I'd be thinking of that shift point on the back straight for 5th and what it would do to you in the Esses. On that backstraight, if you'd have to go to 5th prior to cresting the first hill, it might hurt your speed at the end. If you have to be low in 5th or banging the RL in 4th for the asc. esses, again it might hurt more than help.

We unfortunately cannot carry that hill in 4th - fortunately we can easily take the esses in 5th and can just barely touch the RL entering Oak Tree in 4th. All in all, it's not that bad a trade off but I'd like to know how the times would change if we could crest the hill in 4th. Perhaps it would make zero difference.

 

Good point about the esses Adam. I had (probably intentionally) forgotten about that.

With the stock FD I could flatfoot the esses in 4th gear. After I put in the 4.7 I had to do it in 5th gear. Man, that sucked. I could still do it, but I wasn't going any faster than I was in 4th and I felt like I had no throttle control over the car at all (probably because I didn't have any).
Another example was CMP. Chasing Brinson (again, stock 4.4 FD) around the track he never used 5th gear at all. He was 2/3/4 around the whole track. I was 3/4/5. Again, I had nothing for him once I had to grab 5th gear.

But the 4.7 did pay off in some corners. Usually the faster 3rd and 4th gear stuff. Corners where you'd be in 3rd or 4th regardless of the FD... The 4.7 got me/kept me in the power band alot better.

Again. Its going to be a matter of the tracks. If you plan to run Lowes or Daytona, stay away from the 4.9 (I was running out of gear at Lowes with a 4.7).

If you have a 4.2, you might just want to consider the 4.4 from the GSR (but I thought the LSs had 4.4s). That will allow you to use 2/3/4 and 5th only on long straights in most places.
I think this is what Shultz has decided to do.

 

Adam, Scott,

Good Points!!

At VIR I am in 4th through the uphill esses and flatout with barely a lift. Only use 5th gear as I reach the top of the hill on the back straight and very briefly on the front straight before braking.

At CMP I never saw 5th gear at all.

Maybe I should be looking at a 4.7 or even a 4.4 or as you all have suggested keep the stock FD. The website for gearing calculations shows a 4.266 on 94-01 LS cars.

Majority of racing is done at SP and VIR, with one race each at Beaver Run and CMP.

Regards,

Jon

 

My suggestion would be to get a cheap 2nd hand 4.4 from a GSR and go with that. It'll get you a little higher on the tach without changing your gear selection in 90% of the corners you're currently running.

Don't get me wrong, I'm not saying the 4.7 is *bad*. For the most part I lowered my lap times with it. Its just that I think the gains are minimal and the car is easier to drive/control with the 4.4.
The 4.9 may be the best solution, but I can't say because I never tried it.

 

Well, it looks like the 4.4 might see very marginal gains over the 4.2. Which then begs the question if going to a 4.7 or 4.9 means using 5th gear earlier at Summit and through the esses at VIR.

Considering all the labor to install one and the cost of nearly $800 for a 4.9 (much less for a 4.7) maybe stock is the way to go.

This thread has brought up many good points and maybe doing nothing is the way to go considering the tracks the car will race this season and next.

Regards,

Jon

 

When I had my old 94 RS which is the same box as the LS I was able to drop 3 secs by switching to the 98 spec ITR at Big Willow, now I also got the factory LSD with it so that helped as well.

The point being is that for about 1500 bux for an entire gearbox (not sure on your class legality) you get near perfect track gearing only bettered by the 96 spec (JDM on both) ITR box with the 98 spec 4.78 FD

if you pushing 7600 on your shift points with the stock gearing I would go with the 4.9 however as one poster mentioned this means you might pin it in 5th

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Duke Togo &raquo;</TD></TR><TR><TD CLASS="quote">The point being is that for about 1500 bux for an entire gearbox (not sure on your class legality) you get near perfect track gearing only bettered by the 96 spec (JDM on both) ITR box with the 98 spec 4.78 FD</TD></TR></TABLE>

Not legal for the class.

I vote for the 4.9. Chances are, you won't have the power to run out of revs on the tracks we run. That 4.9, and really any fd for that matter, will help big time looking at your CMP vid. You really seem to "lag" after shifting into 3rd in the auto-x section & at the start.

Best mod I've done on my car yet, seriously.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jason Franza &raquo;</TD></TR><TR><TD CLASS="quote">Best mod I've done on my car yet, seriously.</TD></TR></TABLE>

Ah yes .. but you also have the nice .848 5th gear which actually pulls the car under power. Us GSR boys with .787 and LS boys with .714 have a 5th gear which is not useful for anything other then keeping whatever speed you happen to be going when you selected the gear.

I have only driven my car with the stock 4.4 and after Scott's experience I will save the $1000 and stick with it.

 

But I'm betting the 4.9 has him in 5th gear for the esses at VIR and the Kink at CMP. He doesn't have the power you have (or I had for that matter) and I can tell you that doing both of those places in my car in 5th gear was an exercise in making sphincter diamonds.
The issue is having enough throttle response to keep weight planted on the rear of the car. With the stock 4.4 I could do both of those places with my foot planted and the car felt planted. With the 4.7 I still had my foot planted, but now I was in 5th and I felt more like I was coasting through there. And as you know, "coasting" through the kink or the esses at 115mph isn't such a great idea.

But, the 4.9 might give 5th just enough help to give you that throttle control in those places. If Franza gives it the thumbup its probably worth a try.
Is 5th in the LS the same as in the GSR and ITR?

 

Jason, Scott, Zsolt,


More decisions to ponder.

Jason, if you haven't driven anything with an LS box, you may not be aware of how useless 5th gear is. I know you have raced at Summit. Down the main straight I shift into 5th at about start finish. I go from 7200 rpm's (remember it's not a VTEC) and it drops to 5000 rpms and will not budge from there. I literally coast down the second half of the straight at 5000 rpm's and momentum picks me up an extra 2-3 mph. That's how useless the gear is. The first time I shifted into 5th at Summit I thought I had lost two cylinders, it's that pronounced. It's like you skipped a gear and went from 2nd to 4th gear by accident.

5th gear in an LS is even more useless than in a GSR or ITR. That's why the Turbo boys love these gearboxes on their modded street cars.

If we could legally swap out 5th for something more useful like a .884 it would make a huge difference but we have to retain stock gearing in HC.

I may end up being in better shape with a stock FD since I will be able to be in 4th most places, where the new FD puts me in 5th. In other words the time I gain in the first 4 gears will be lost when I have to shift into 5th.

There is no way I would want to go through the kink with my crappy LS gear. There would be no way to put down enough power to keep the rear planted.

Boy it must be nice to be a top running SWC team where you just test the living crap out of every combination until you get the right one.

Right now it appears that I have a competitive car and last thing I want to do is make the car slower. Might wait until after Beaver Run and the first Summit race to decide.

 

I don't know if it is leagal in yoru class or why it was no considered (and it is off topic but..)

For 800 bucks for your 4.9 final drive in a LS gear box.....why not just get a new gear box from a b16a2 or a b18c5...they have shorter gears which will solve your problems, you will have to re learn how to drive with such short gears but for the cost of the FInal drive i don't see how your can try and solve a gear size issue with the final drive.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B HATCH &raquo;</TD></TR><TR><TD CLASS="quote">I don't know if it is leagal in yoru class or why it was no considered (and it is off topic but..)

For 800 bucks for your 4.9 final drive in a LS gear box.....why not just get a new gear box from a b16a2 or a b18c5...they have shorter gears which will solve your problems, you will have to re learn how to drive with such short gears but for the cost of the FInal drive i don't see how your can try and solve a gear size issue with the final drive. </TD></TR></TABLE>

We can't switch gearboxes in HC. We have to keep stock gears and stock tranny. The only thing that we can fiddle with is the final drive which can be from any production Honda/Acura.

With most gearboxes, switching to a higher final drive like Jason did gets you much better acceleration and works fine as long as you don't lower your top speed below what you run at your fastest track.

The GSR and ITR trannys don't face the same dilema that the LS box with it's "overdrive" 5th gear does so it less of a tradeoff.

Regards,

Jon

 

You could save a *little* money (around $150) on the 4.9 by going with the SRR gear over the ATS.

 

The first time I shifted into 5th at Summit I thought I had lost two cylinders, it's that pronounced. It's like you skipped a gear and went from 2nd to 4th gear by accident.


The exact same thing happened to me back in about 1998 when I visited Roebling Road for the first time. Previously I had only used 5th gear on the back straight at Road Atlanta, and that was downhill and briefly.
The first time I hit the front straight at Roebling (stock 4.4 FD) there was a fairly significant head wind. I hit 5th gear about 2/3 down the straight and the car actually SLOWED DOWN. I lost about 2 or 3 mph by the time I hit the braking zone. I discovered I could turn better lap times (this was a Solo I) by just riding the rev limiter in 4th.
The 4.7 helped this out alot. The car would pull decently in 5th gear. But the Kink and the esses... .

So, to summarize:
For a RS/LS/GSR, the 4.7...
Is great for long flat (or downhill) straights and slower 3rd gear corners.
Is not so great for fast sections or uphill straights.

 

"You could save a *little* money (around $150) on the 4.9 by going with the SRR gear over the ATS."

it's funny that the some of the FD upgrades are Isuzu parts rebadged and sold at 3x the price at least in the s2000 application

 

Good points Jon/Scott/Zsolt. Yeah, I've driven them both and I know 5th is a dog. That's a tough one. Yep, 5th in the esses (damn that's fun), and in the kink.

Hopefully someone that's tried your particular tranny equipped with a 4.9 will see this and offer an opinon.

 

Jon, if I am using the right gear values, it looks to me like you would be at ~140 mph in 5th at 7200 rpm with a 4.9 FD. Whereas I don't think you'll hit that anywhere (even LMS) realistically, I don't know how adverse the effect of the gearing change - seems like you are essentially going to a 5sp from a 4sp. I have a little application for playing w/ these numbers that might be fun to play with, shoot me an IM if you want me to send it (has a text file w/ the gearing stuff in it - but I do not guarantee its accuracy).

I am seeing:
1st @ 7200 rpm: 35.5mph
2nd @ 7200 rpm: 60.4mph
3rd @ 7200 rpm: 90.4mph
4th @ 7200 rpm: 118.7mph

does this sound about right?

 

You can also use the online calculator at Housemanautosport.com. I've found it to be very accurate.

Mu only point is that if he is mainly concentrating on Summit and VIR, with a little CMP thrown in, I think he's better off just staying away from 5th altogether (unless hes on a downhill straight, like the ends of the VIR and Summit straights). The 5th in my GSR was terrible and it looks like his is even worse, and to make it worse he has less HP to work with.
Imagine the difference on the front straight at VIR between going to 5th after the S/F line or going to 5th at pit entrance. If you can't imagine it, I'll help you... the difference is HUGE.
And again... The esses. Even with the 4.9 I think that 5th gear with that HP would be one hairy assed ride.

Of course, Jon just could buy 4 trannys, each equipped with a different FD, and rent VIR for a day to answer all these questions .