MDL-01C5

The next step for me is gears... what makes one ratio better than another other in any given application?
Knee-jerk says that 4.10's are best, but the others are there for a reason, right?
I'm wondering if RPM limit has something to do with it?
Mine is maxed at 7000.
Also, my power and torque come late--at 3200+
so what do you think would work best for me?

Andy West

Generaly speaking each .10 on the gear ratio,
it is worth almost .10 in the 1/4 mile time. (up to 4.10:1 then the higher the gear starts to make less and less of a difference) So 3.73 should make your car .3 seconds faster then 3.43
4.10:1 should make your car .30 seconds faster then 3.73:1

Of course this is NOT an exact sience. Just a general estimate I have seen some pro's use.

If you want 3.73:1 or 4.10:1 would depend on how much of a daily driver the car is.
And the higher the gear the harder it is (generally) on your drivetrain,etc.

Yes, gears have ALOT to do with RPM. The higher the gear the faster the RPMs will wind up.
That is what makes it good for the 1/4 track.
But 4.10:1 is going to kill your gas mileage, and will reduce your top speed. But if you are most worried about the track, then 4.10's are good.

Personally I am going with 3.73:1 because my car is more of a daily driver then it is for the track. 3.73 seems more street-friendly to me.
And I use to drive from Upper New York to Kentucky, to and from, twice a year.
I dont know anyone that wants to do that on 4.10's!
I like the best of both worlds.
I'm guessing your vette has 3.42:1. So I would predict a .3 second increase if you get 3.73's and around .6 second increase if you get 4.10

But yet again, there is alot of varibles in this estimation.

<img border="0" alt="[Corvette]" title="" src="graemlins/corvette.gif" />

MDL-01C5

Hey Andy-- thanks for the quick reply...
The car is a daily driver, but only in-town...I have another car for long distance driving.
I'm primarily interested in the track gains, but I'm also curious to hear from anyone who's running 4.10's around town...
How's it behave? Can it be considered "close" to streetable for daily use?
I'm leaning towards them, but would still be interested in further opinions on selection and characteristics.
Thanks
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Slow Z28

iTrader: (19)

i got 4.10's in my 2001 SS. stil stock motor just some bolt ons. i feel that the 4.10's make the car more driveable. what i mean by this is that 5th gear around town is more usuable and 6th gear on the freeway isn't lugging down real low. i have never driven a car like thiswith 3.73's, so i couldn't tell you the difference between the 4.10's and them. but one thing is for sure, first gear is really short <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Chris

MDL-01C5

So as a daily driver it's not so bad...

FASST

General rules for gears--for use at the track, states that you should run through the trap at redline in your 1:1 transmission gear. With that in mind, check out your past runs--this will give you an idea of what kind of MPH you're hitting. Go slightly higher than that MPH (you'd like to think that you'll get faster with gears!) and calculate what final drive ratio you need to hit that mph. Generally, it's not all that useful to run aftermarket gears in a stock redline car, because you'll be forced to shift into OD to finish the 1/4 mile. Since you've obviously rasied your rev limiter (I'm assuming due to the addition of a cam--maybe heads too--and programing) you should be able to use the benefits of gears. One thing you might want to consider is that the higher the gear ratio, the weaker the gear strength. If you're running slicks with 4.10s, you'll need to be somewhat careful on your launches. As far as daily driving goes, 4.10s are completely streetable as long as you're not sitting on the highway for extended periods of time.

Andy West,
I think your gear gains are a bit aggressive. I've seen generally about ~.10s increases for people that jump from 3.42 to 4.10s. I'd love to see 0.6s, but I surely wouldn't expect results like that.

MDL-01C5

Yes, I've got a H/C and programming.
Well, I'm maxing out 3rd gear right as I cross the 1/4-- at about 68-6900RPM crossing the line, with a 7000 limit. peak is about 64-6500, but that late, there's no use in trying to shift.
Based on that, with 3.42's, what do you think would be optimum?

<small>[ May 06, 2002, 02:44 PM: Message edited by: MDL-01C5 ]</small>

Jadeeglide1550

Don't forget... if you go to the 4.10's.... or the 3.73's and use fourth gear... which is the 1:1 gear in the six speed.... you will lose some time making the 3rd to 4th shift... So... you may be better off with the 4.10's than the 3.73 as you will have more time to use fourth gear. If you shift into to fourth with the 3.73's and are just about crossing the end of the track... then the use of 3.73's may not gain much. Good luck with whatever you choose......

FASST

jadeeglide 1550 makes a good point. Remember, you want to trap at the top of 4th. So it sounds like the 3.73s won't be deep enough for you. Swapping from the 3.42s to 4.10s will drop your mph/rpm ratio to 83% of your current value. Whatever your current speed equals at redline in 4th gear will be 83% of that value with 4.10s (91.7% with 3.73s). If this speed is lower than your current trap (I doubt it is), 4.10s are too deep. I don't have the gear ratios sitting in front of me for the t-56, otherwise I could just do the whole calc. for you. I hope this helps.

MDL-01C5

I've never made it to the top of fourth(exept at the dyno, where I wasn't paying attention to speed)so I couldn't tell you what that is, but I cross the traps at 116.89 now, and it needs to be noted that in a few weeks, I'll be switching to significantly better heads, so I expect that # to go up an appreciable, though not dramatic, amount.
It's looking like 4.10's may be the way to go, but I'm still curious about 3.90's... is there a way for me to predict anything using the numbers I now have available?
I suck at math, so a formula to me is a Trans Am variant

Freak

you want the engine at HP peak when you cross the traps, so add about 2 MPH to the trap speed, then choose the gear that puts you at your peak at that speed.

Andy West

Byron,

I do agree that what I said does seem exagerated.
IT does to me too. But like I said, Thats just what I've seen professionals say. I have also seen something close, but alittle less aggressive x.10 on a gear equaling .07 in the 1/4. But maybe this is affected by how much horsepower one has. Im sure the difference in gears is less in a 300 horse engine compared to a 383 blower motor. Maybe I am wrong but I can kind of see how a x.30 change of gear could equal a .07 difference in times if it is a very powerful car.

However I am intrested to hear how much of a difference it made on some of us with more humble cars.

FASST

Andy,

My numbers from people running around our range (350-500hp). Some of the professionals live in a surreal world I can only imagine--in which case they might see those numbers. Cheers.

Fulton 1

iTrader: (9)

A piece of shareware that I've found useful when playing around with gear ratios is Cartest. You can download it from Richmond Gear's website www.richmondgear.com/downloads.html

With it you can pick a car, make adjustments for traction, gear ratios, shift time, horsepower curve, etc. and then look at the theoretical performance changes.

Might be of some use...

MDL-01C5

Thanks Fulton--that's a cool little DOS program <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />