Gears:1/4 mile times....

[CobraKevin]

My dad always gets on me about changing my gears back to the stock 3.55's and says the 4.10's made the car faster. He thinks of there was another car just like mine with the same HP and same skilled driver, the other guy with 4.10's would win. I think the opposite. Anyone wanna shed some light on this topic? What exactly does changing your gears do i.e. what happens when you go to a higher or lower gear setting? Would the type of tire you were using have an effect on how well a certain gear worked out? I really would like to get this figured out.

[Guest Ranger_Man]

higher gear means less acceleration but more top end. if you raced another 03 cobra with the same mods with a driver with comparable skills you will lose from a dig. however, you will start coming back in the upper end of the speedo as you will stay in your powerband longer.

 

lower gear is for higher acceleration but takes away top end due to running through the rpms faster and therefore also forces more shifts.

 

what you need to do is find a good medium between higher and lower gear ratios. if your gear is too high you will fall out of your powerband every time you shift. on the opposite hand, if your gear is too low you will run out of top end too quickly. drag racers will tell you to find the gear that puts you just shy of your top end as you cross the traps. however, this is usually a bad set up for the street as at cruising speed your rpms are rediculously high.

 

moral of the story, you will be fine with your current gear, and by saving that money you can put it into something else in the car.. e.g. suspension.

[COLD AIR]

High gear = lower # as in 2.73

 

Low gear = high # as in 4.11

 

For a 1/4 mile race you want the rpm to be at red line( or ware ever rpm you start to lose power)in top gear- not overdrive-

Lets say 6000 is your shift point and you need to go through the traps at that rpm. You need a gear that puts you at that RPM @ 1320'

If 4.11 put you there, rpm's@1320, thats what you need. If you get to that point at 1000' you need a lower # gear

If you have 3.55 and your at 5000rpm @1320 you will be .3 slower than with 4.11

[CobraKevin]

With my 4.10 gears, I was hitting the rev limiter in 4th just as the win light came on. This was netting me 12.3's on street tires. So Chris, you're telling me that I would run 12.6's with the gear that I have now? I would think, given the power my car has, I wouldn't need help from gears to get me into my powerband, and therefore the top end power of my gears in 3rd and 4th would be enough to gain back and gain some ground on whatever was lost in the first two gear from the steeper gear. I mean, my 4.10's obviously got me to the top of 2nd quicker than the 3.55's, but that's only 60-65mph with the 4.10's and 75mph with the 3.55's. I mean, we'll see the results next season, but since I do plan on putting headers on, I'll need the higher gear anyways. But at the Modular Shootout, I don't remember any of the 5 or so faster than me with 4.10's.

[kenny]

Chris already covered it.

 

Also, remember that a lower gear (higher numerically) will make the car easier to move (more torque multiplication). Think of riding a ten speed, if you start in first gear it's very easy to pedal. If you start in tenth, it's next to impossible.

[Dave1647545494]

you can get some gear back by running a smaller tire as well. if your tire on the car is say 28-29 inches in diameter and you switch to a 26 inch tire it will be like going from a 3.55 to a 3.73 you also have to make the car what you want. if its mostly street driven the drivetrain will last longer with a 3.55 than with a 4.10 because it will take less rpm to go the same speed.

[ORourke]

You'd be quicker with 4.10's. Why would so many people swap in lower gears if it made you slower? The big advantage is off the line. Gears will really help a motor that makes power higher up in the RPM's. You'll get in the power band faster and stay there on the shifts.

It won't make as much of a difference on a car like yours that makes a bunch of power down low, but it's still a mechanical advantage.

[CobraKevin]

Originally posted by slowgreencar:

You'd be quicker with 4.10's. Why would so many people swap in lower gears if it made you slower? The big advantage is off the line. Gears will really help a motor that makes power higher up in the RPM's. You'll get in the power band faster and stay there on the shifts.

It won't make as much of a difference on a car like yours that makes a bunch of power down low, but it's still a mechanical advantage.

The off the line thing is what I was wondering about. Most people that change their gears to get great track runs, mainly on slicks, which is why I was wondering if the type of tire made a difference. But since the 3.55's have better top end, would the outcome be reversed from, let's say, a 40 roll?

[SamZman]

Originally posted by No Longer NA Cobra:

The off the line thing is what I was wondering about. Most people that change their gears to get great track runs, mainly on slicks, which is why I was wondering if the type of tire made a difference. But since the 3.55's have better top end, would the outcome be reversed from, let's say, a 40 roll?

Going from a 40 roll the 4.10 gear would still have the advantage. The only time a 3.55 gear would be better would be if you were going for all out top end, or if the 4.10 gear would cause you to run out of 4th gear at a drag strip. There seems to be misconception that a 3.55 gear would be better on the freeway than a 4.10 gear. I guess that's cause some people would call the 3.55 a "highway gear" because of increased top speed.. Fact is a 4.10 gear will be faster at any speed till the car tops out..

 

If you were right at red line at the end of the 1/4 w/ the 4.10's that sounds perfect. Of course if you made any more hp you'd be running out of gear and forced to shift to 5th(which generally kills ET).. but then like someone else mentioned you could go to a little taller tire to solve that problem while also adding traction.

 

Anyways.. your dad is right graemlins/slap.gif

[90gt]

A 4:10 gear I would say is more for a na car then a blower car. I know of two different cars that picked up from going from 3:73's to 3:55's and 3:27 it just depends on where the power band is. On a roots style car like your 03 Cobra I would leave the 3:55's in it because you don't need as much torque multiplcation with a roots style supercharger because where the power comes in. I know of a supercharged mustang that picked .5 seconds from going from a 3:73 to a 3:27 like a well known performance shop recommended.

[SamZman]

Originally posted by QWK90GT:

I know of a supercharged mustang that picked .5 seconds from going from a 3:73 to a 3:27 like a well known performance shop recommended.

Maybe the Mustang should put 2.73s in and pick up another 5 tenths? tongue.gif I think it's vague statements like that, that are confusing people. There are many different variables which need to be considered such as redline, tranny gearing, tire size, etc..

[Guest stevil]

Originally posted by No Longer NA Cobra:

With my 4.10 gears, I was hitting the rev limiter in 4th just as the win light came on.

That sounds pretty good. With the 3.55s you'll be crossing the traps about 1-2K rpms less in 4th or something. But what if you got 3.23s and crossed the traps at the top of 3rd? tongue.gif

[90gt]

Originally posted by SamZman:

Maybe the Mustang should put 2.73s in and pick up another 5 tenths? tongue.gif I think it's vague statements like that, that are confusing people. There are many different variables which need to be considered such as redline, tranny gearing, tire size, etc..

I just put that situation because roots style superchargers don't really need as steep of gear as most other cars would is all.

[Amy]

I agree with QWK90GT, a 4:10 maybe would be ood for the track, but I would leave the stock gear in, so you can play on the freeway and have top end, plus your gas mileage will be better... just a thought

[CobraKevin]

Well, I didn't plan on changing the gears back to 4.10's anyways, I was just seeing what people thought on the subject. I'm going to be putting headers on hopefully in the spring, so I'd need a shallower gear like the 3.55's anyways.

[OGRE]

Originally posted by AmysBAD98GT:

I agree with QWK90GT, a 4:10 maybe would be ood for the track, but I would leave the stock gear in, so you can play on the freeway and have top end, plus your gas mileage will be better... just a thought

I agree that a new cobra doesn't need any more gear just not for those reasons.

6th gear is taller than 5th in your car, and his theoretical top speed in that gear is over 180mph with a 4.10 gear. there is no top speed loss , and at 70mph in 6th his motor will only be spinning 2350rpm.

 

 

Originally posted by QWK90GT:

I just put that situation because roots style superchargers don't really need as steep of gear as most other cars would is all.

I agree. another reason to keep 3.55 in is if 3rd gear is tall enough that he doesn't have to shift into 4th before ending a pass at teh track. In that case the extra shift of a 4.10 may negate the difference in tourque multiplication.