Final Drive gears??

[cdrazic93]

Originally Posted by KoolBRZ

Think before you speak. I've actually changed my FD. Have you? Any idiot can spew insults. I back up what I say with fact. Care to dispute that?

you can scientifically prove that the brunt of the torque force vector is shifted from the driveshaft to the axles? please show me.

[KoolBRZ]

Originally Posted by cdrazic93

you can scientifically prove that the brunt of the torque force vector is shifted from the driveshaft to the axles? please show me.

Easily. First the ratio of mechanical advantage the axle has turning the wheel is set by the size of the tire diameter. Second, the ratio of the Final Drive, (FD), sets the mechanical advantage the driveline has over the axles. Changing the FD from 4:10 to 5:10 gives the driveline more of a mechanical advantage over the axles, since the driveline turns more revolutions for the same number of axle revolutions, and since the tire size hasn't changed, the axle still has the same mechanical advantage.

[Apoc]

Originally Posted by KoolBRZ

Think before you speak. I've actually changed my FD. Have you? Any idiot can spew insults. I back up what I say with fact. Care to dispute that?

Nope

[HUNTERANGEL121]

Originally Posted by KoolBRZ

Yes it actually does. While it doesn't change the gears themselves, it does change the spread between the gears. The gearbox isn't used by itself. It works BETWEEN the engine and the differential. The gear spread, which is the difference between close ratio and wide ratio gearboxes, is dramatically affected by the FD ratio.

In simple words, the redline speeds in 1st thru 6th with a lower FD ratio will be further apart, in other words, a wider spread. For example;

4:10 ratio lower = farther apart
1st=38 MPH @ 6966 RPMs
2nd=63 MPH @ 6969 RPMs
3rd=89 MPH @ 6933 RPMs
1st - 2nd, 25 MPH. 2nd - 3rd, 26 MPH

5:10 ratio higher = closer together
1st=30 MPH @ 6841 RPMs
2nd=50 MPH @ 6880 RPMs
3rd=72 MPH @ 6977 RPMs
1st - 2nd, 20 MPH. 2nd - 3rd, 22 MPH
If you're shifting closer together, it's the same as saying it has a closer ratio between gears.

Just gonna chime in. Gear spacing would remain the same. But you mention how you're now shifting closed.

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[gramicci101]

Originally Posted by KoolBRZ

The gear spread, which is the difference between close ratio and wide ratio gearboxes, is dramatically affected by the FD ratio.

Again, wrong. Absolutely wrong. You're telling me that the gear ratios in the transmission are moved closer together by changing the ring and pinion. That 5th gear at 1.000 is somehow magically closer to 6th gear at 0.767. Without actually changing 5th and 6th gears, just changing the ring and pinion. Do you listen to yourself, because no one else does.

A close ratio transmission is called a close ratio transmission because the ratios are, hint hint, closer together. Has nothing to do with anything outside the transmission. Not the ring and pinion, not the tire size, not the engine speed, not the ground speed, not what color socks you wear that day. The ratios in the transmission. Only. You physically change 6th gear from 0.767 to 0.850 and leave 5th at 1.000? Guess what? They're closer together.

Originally Posted by KoolBRZ

If you're shifting closer together, it's the same as saying it has a closer ratio between gears.

No. No it's really not. I'm sorry you can't understand this.

Originally Posted by KoolBRZ

Think before you speak. I've actually changed my FD. Have you? Any idiot can spew insults. I back up what I say with fact. Care to dispute that?

The facts you back yourself up with are wrong and only make sense to you. You've changed a whole lot of stuff that makes absolutely no sense at all to anyone. Anywhere. If you'd have only thought first before actually making changes you could have saved yourself a whole lot of money.

[stevesnj]

Well whatever you decide just remember that increasing the horsepower which essentially raises torque it does so with a drivetrain that was designed to be most effective with the stock HP and torque values. These cars were also developed to be easily modded (Scion PR) but modded within reason. It's easy to throw FI or nitrous on there but fail to understand that the parts connected to the engine just are not within over modded specs. Then there are threads asking why I keep breaking axles or grinding up rear gears with a 600 HP engine. These are the consequences of not researching enough. I would find out what DS, U-Joints, Gear Set, Axles, brakes, tires etc. to take the extra torque. Looking forward to seeing your decision!

[wparsons]

Originally Posted by KoolBRZ

Yes it actually does. While it doesn't change the gears themselves, it does change the spread between the gears. The gearbox isn't used by itself. It works BETWEEN the engine and the differential. The gear spread, which is the difference between close ratio and wide ratio gearboxes, is dramatically affected by the FD ratio.

In simple words, the redline speeds in 1st thru 6th with a lower FD ratio will be further apart, in other words, a wider spread. For example;

4:10 ratio lower = farther apart
1st=38 MPH @ 6966 RPMs
2nd=63 MPH @ 6969 RPMs
3rd=89 MPH @ 6933 RPMs
1st - 2nd, 25 MPH. 2nd - 3rd, 26 MPH

5:10 ratio higher = closer together
1st=30 MPH @ 6841 RPMs
2nd=50 MPH @ 6880 RPMs
3rd=72 MPH @ 6977 RPMs
1st - 2nd, 20 MPH. 2nd - 3rd, 22 MPH
If you're shifting closer together, it's the same as saying it has a closer ratio between gears.

90% wrong. Changing the FD will change how fast you go in a given gear (that's all you got right), but it will not change the RPM drop between gears at all.

Close ratio gearboxes are just that, the ratios between gears are very close to each other. You can have a close ratio gearbox with a very tall final drive, just like you can have a wide ratio gearbox with a very short final drive.

You want a close ratio for narrow powerbands because it lets you keep the RPM in the meat of the powerband. You want wide ratio for huge flat wide powerbands because you'll be shifting less but still keeping the engine in the meat of the powerband.

[KoolBRZ]

Read before you reply, you ASSumer. I said it doesn't change the gears themselves. If you would take your blinders off, you would see what I mean. I'm talking about the change in ratios between the engine, the source of power, and the destination, the tires on the road. I clearly spelled out the change in redline peaks per gear when changing FD's. You just ignored that and spewed idiotic insults because you thought I was just talking about the gears in the transmission itself. If I was just talking about gear ratios in the transmission itself, why show engine RPM's? I've been talking about the overall ratios between the engine and the tires.

The OP who started this thread clearly said the trans could come with different ratios, so, unless he does some calculations he isn't going to know where his redline peaks are without mounting it in the car. With a 500 HP engine he clearly isn't concerned with MPG, but, he is concerned with drivetrain reliability. The existing parts are balanced for a 200 HP engine, a 6 speed close ratio manual transmission, a 4:10 FD, and a 27.25" diameter tire. Change any one of those and the balance changes. More pressure will be put on some components, and less pressure on others. That is what the OP wants to learn about. This is the kind of secret information drag racers know about, but don't talk about with the competition. Here are some links that can help the OP with the decision he's going to have to be making.
http://www.ek9.org/index.php?threads...-friend.10883/
http://www.csgnetwork.com/multirpmcalc.html
and of course, http://weirperformance.com/finaldrivegears.html

[HUNTERANGEL121]

I think this all went downhill when someone asked about gear spacing...

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[Ultramaroon]

Originally Posted by KoolBRZ

That all depends on the ratios in the gearbox. Why don't you just install it first, then change the final drive to suit the gearbox? Remember, the lower the FD ratio, the more torque is put on the drive train, the higher the ratio, the more torque is put on the axles and wheels. Do you need top speed, or top acceleration? That sequential gearbox will give phenomenal acceleration with a high ratio FD because it will make the gearbox a close-ratio gearbox.

No. All the components leading up to the diff see the same torque. There is no magical potion to create and apply torque upstream of the change.

Originally Posted by KoolBRZ

Yes it actually does. While it doesn't change the gears themselves, it does change the spread between the gears. The gearbox isn't used by itself. It works BETWEEN the engine and the differential. The gear spread, which is the difference between close ratio and wide ratio gearboxes, is dramatically affected by the FD ratio.

In simple words, the redline speeds in 1st thru 6th with a lower FD ratio will be further apart, in other words, a wider spread. For example;

4:10 ratio lower = farther apart
1st=38 MPH @ 6966 RPMs
2nd=63 MPH @ 6969 RPMs
3rd=89 MPH @ 6933 RPMs
1st - 2nd, 25 MPH. 2nd - 3rd, 26 MPH

5:10 ratio higher = closer together
1st=30 MPH @ 6841 RPMs
2nd=50 MPH @ 6880 RPMs
3rd=72 MPH @ 6977 RPMs
1st - 2nd, 20 MPH. 2nd - 3rd, 22 MPH
If you're shifting closer together, it's the same as saying it has a closer ratio between gears.

Originally Posted by KoolBRZ

I just did.

No, it is absolutely 100% not the same. You are not shifting closer together. I am becoming personally offended by the complete rubbish you are espousing as fact to innocent people who are coming here for advice.

Originally Posted by KoolBRZ

Think before you speak. I've actually changed my FD. Have you? Any idiot can spew insults. I back up what I say with fact. Care to dispute that?

The final drive ratio has absolutely nothing to do with the ratios of the gearbox itself. You are confusing your butt dyno with fact. Again, please stop and first read something authoritative.

At least we the community consistently push back against your misguided poke-and-hope approach. Hopefully you will realize the danger of your hubris before someone gets hurt.

[KoolBRZ]

Who said I was talking about gear ratios? I'm talking about the ratios between the engine and the tires. I'm also not talking about torque, but about mechanical advantage between components. Check out the links I posted before you assume I'm providing misinformation. Your negative assumptions only hurt yourself. What help are you with your criticisms? I provided helpful links. While you can only criticize in a vain attempt to make yourself look better. The OP wants help, not critical, self-serving, negative crap.

[cdrazic93]

Originally Posted by gramicci101

Are you really saying that changing the ring and pinion in the differential will make the gear ratios in the transmission closer to each other? Do you think before you speak, or do you just open your mouth and roll with whatever comes out? Why don't you try to sell him on removing the left swaybar and welding the header closed too?

Originally Posted by KoolBRZ

Yes it actually does.

To be fair that post said yes, then you unknowingly explained why the gears (actually) dont change, slightly confusing.

[HUNTERANGEL121]

How about this... You're all speshal snow flakes. But this arguing is kind of annoying.

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[cdrazic93]

Originally Posted by KoolBRZ

Remember, the lower the FD ratio, the more torque is put on the drive train, the higher the ratio, the more torque is put on the axles and wheels

Originally Posted by KoolBRZ

I'm also not talking about torque, but about mechanical advantage between components...The OP wants help, not critical, self-serving, negative crap.

You talk like torque and mechanical advantage as the same thing...

Usually people like it when the help is mathmatically (you got that stuff down) and physically correct (you need to do some more learnin and a readin).

Why is it if you correct someone a few times on the internet they get all pouty and call you negative and get their jimmies in a bunch? Sheesh.

A man must be big enough to admit his mistakes, smart enough to profit from them, and strong enough to correct them.