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Final Gear Ratio

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J

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Discussion Starter · #1 ·
Im installing a lightened flywheel...and since my tranny is coming apart I was going to upgrade to a higher final gear ratio. My question is what ratio should I go with...and how much of a acceleration will I gain? Is it different in all the gears? And are there any pros or cons in doing this?

Whats the difference in getting a final gear ratio than getting new 3rd, 4th, and 5th Gears - 1.652, 1.308, 1.033 ratios? I was looking at ATS products...any experiences?
 
K

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#2 ·
A higher numerically final drive will give your more torque multipliction in all gears and will raise your engine rpm's in all gears. Higher numerically final drive = better acceleration, lower top speed, higher engine revs, more engine wear, lower gas mileage. For average street car, more wear and lower gas mileage is true, might not be true for some specific applications. These are generalities. Changing just say, 2nd gear, would only change things for that particular gear.
 
T

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#3 ·
better accleration depending on what kind of race you do...

drag? forget it
auto x or road racing? go for it

changing second gear woudln't just "change second gear".. .. u'll most likelye dropping out of your powerband when you hit third.. u'd want to change the gears in accordance with the type of racing you do
 
K

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#4 ·
My second gear answer is indeed correct. If only the gear ratios in second are changed, then only the gear ratios in second are changed. I am not saying that changing only the ratio in one gear is bad. If the engine only drops out of the powerband in second then changing only it would be a good idea. The car would indeed accelerate more quickly overall, due to the change in second. The acceleration would be the same in the other gears, all else being equal. Why do you suggest changing gear ratios only for auto x or road racing?
 
T

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#5 ·
kelly on Aug/03/02 said:
My second gear answer is indeed correct. If only the gear ratios in second are changed, then only the gear ratios in second are changed. I am not saying that changing only the ratio in one gear is bad. If the engine only drops out of the powerband in second then changing only it would be a good idea. The car would indeed accelerate more quickly overall, due to the change in second. The acceleration would be the same in the other gears, all else being equal. Why do you suggest changing gear ratios only for auto x or road racing?
Click to expand...
because in drag, the stock gear ratio is good enoguh.. spending 700+ on gears or final drive isn't gonna help you in your 1/4 time..

lets u change your seoncd gear ratio so that its closer to first.. your MPH at redline in second gear will be lower than before.. okay, now third comes up... you think u'll land in the same spot in third? no, u'll land in LOWER rpms due to lower MPH from second..

when honda designed the stock tranny, they did a really good job of designing the gear ratios..
 
S

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#8 ·
Thats not necessarily true.. Might be for our beloved integras, but my friend has a SC cobra, and he put 4.10:1 gearing in it, before the supercharger and it made his car a lot quicker, and when he picked his car up after having the SC put on, the guy reccomended a 3.88:1 gearing, to make it even quicker.. Like I said, this is on a cobra, integras might be, and probably are different, But this thread caught my eye because Ive been thikning about gearing alot lately..

Oh, and on gran turismo 3, I did the lowest gearing I could and it made my car a few seconds quicker

(yes, I know real life doesnt compare to GT3)
 
MichaelDelaney

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#9 ·
In drag racing the hole shot is the key. Even with a stock 4.40:1 FD you have to shift from 1st -> 2nd before the 60 ft mark. This shift slows your 60 ft time and hole shot and can be a nuisance due to added wheelspin with the short 1st gear. If you add a shorter JDM 4.78:1 FD or an ATS 4.91:1 for acceleration it will make the 1st gear even shorter and compound this problem at 60 ft. The aftermarket gear sets from Japan like the Kaaz or ATS have taller gear ratios in the first 2 gears so you can launch and go without having to shift until well after 60 ft.

If you get a shorter final drive, you should get a taller 1st to minimise the holeshot and wheelspin/wheel hop issues. The shorter gear in 3rd should help you accelerate faster and keep you in the powerband after the 2nd-> 3rd gear shift.

Remember you get these to ensure you stay inside your powerband after a shift (drag or road race). That's the reason to get it.

You can convert the GSR tranny into a ITR tranny by just adding the JDM FD.
 
J

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Discussion Starter · #12 ·
I finally see how gear ratios can really affect the acceleration of a car. Your post of the graphs really made my decision and I am definatrly goin for the ITR final gear ratio. Thanks, I learned a lot.
 
V

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#13 ·
thats really interesting.. im wondering now that since we exchange parts with the b-series motors.. what can we do about trannies?i do mostly street driving and drag racing, although road-racing is not out of the question. im looking at a setup that maximizes my 0-60mph. and shifts after that. what would happen if i took an LS 1st gear and gs-r second/ 3rd, itr 4th, gs-r 5th, added the 4.40 FD... you get the idea..

im asking this because i have a 93 integra. the tranny i currently use is the y1 LSD. it comes with a 4.226 FD. BUT, i have my stock LS (4.226) tranny as well as a J1 (4.40) laying around. anyone know what i could do with these three by mix and matching the gears?

i was just going to try the ls 5th and the lsd into the j1.. but maybe theres more that i can do to help my acceleration times. thanks
 
S

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#14 ·
My plan is to drop a JDM or ATS FD into my R, then replace 1st with a taller gear. Not only does making 1st taller improve your 60ft time, it also decreases the space from 2nd gear so you do not shift out of the powerband. Definitely the super short 3.23 first gear has to go if you have a shorter FD. First gear is almost unusable as it is on my stock tranny, I couldn't imagine what would happen if I replaced my 4.4 FD to an ATS 4.9 unit.
 
S

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#17 ·
kelly on Aug/04/02 said:
How can GSR trans be converted to ITR stats by only changing FD?
Click to expand...
You can artifically shorten all your gears by changing the FD. Here's a comparison of the gear ratios of a GS-R w/ JDM ITR 4.785 FD with USDM ITR stock gears.

GS-R w/ 4.785 FD - USDM Type R stock

1st: 3.513 - 3.230
2nd: 2.066 - 2.105
3rd: 1.479 - 1.458
4th: 1.124 - 1.107
5th: 0.856 - 0.848

These ratios are comparing the gears as if they were using the same FD calculating (GSR gear x 4.785) / 4.4. In this example the gearing works so that the GS-R is actually using a 4.4 FD with those gears, mathematically it would equal a GS-R on stock gearing using the 4.785 FD.

As you can see the JDM ITR FD shortens all the gears on the GS-R pretty close to what the USDM ITR has excluding first gear. You can also see here why you'd want a taller first gear when using a shorter FD, as first becomes ridiculously short and pretty much unusable in racing situations.
 
K

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#18 ·
The overall gear multiplication would be changed by a constant by changing the FD. The spacing between the gears would remain the same because only the final drive was changed. Changing the final drive on a GSR will not convert it to ITR stats; it will convert it to a GSR transmission with a different final drive. That is my only point. I understand all the other posts. I shouldn't have stated it as a question. The overall gear ratios should be calculated for accurate results.
 
MichaelDelaney

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#19 ·
if you do the final reductions of the final drive here are the numbers (gear ratio x FD): 1st->5th

GSR 4.4 FD: 14.212, 8.360, 5.984, 4.5496, 3.463

ITR 4.4 FD: 14.212, 9.262, 6.415, 4.871, 3.731

GSR 4.7 FD: 15.456. 9.092, 6.508, 4.948, 3.765

If the 4.7 FD doesn't bring the multiplication factor closer to the ITR's, I don't know what else will.

The GSR will have a ***** of a time getting out of 1st without wheelspin with that short a gear ratio multiplication and won't pull as hard in second but will be close...it'll have a higher rpm after a shift in 3rd to 5th in comparison...

For the 1/4 mile, you'll have 4 distinct shifts like the ITR instead of just having to shift out of 3rd into 4th right at the 1/4 mile mark or a c**t hair earlier using the GSR 4.4 FD tranny.
 
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