GTstangB.F.D.M.

oooo.. ic.. but what about the 3.90's?.. bc one day (like 10 years from now.. lol) i would like to get blown.. so that might be a good median..

even tho by that time.. i would prolly be ready for new gears anyways

.boB

Gears are like a lever - they multiply the applied torque. A longer lever will apply more torque, so a higher gear ratio will apply more torque to the pavement. More torque gives you faster take off and better acceleration. That's why they feel so much better.

A dyno measures torque, and calculates hp. The more torque you apply to the dyno rollers, the better the numbers look. But, the goal of a dyno is to measure engine out put. The real purpose is for tuning and such. With that in mind, you would want to eliminate as many variable as possible. That's why most dyno runs are adjusted for temp, humidity, altitude, etc. Otherwise they would be useless for comparing changes.

One of the adjustable variables is the rear gear ratio. The dyno operator inputs that number, and the computer makes the adjustment. With that adjustment in place, you would see no change between one gear and the other. But, you could always have the operater use the old values for gear ratio. Then you'd see the differance.

ohfiveride

theoretically wouldnt it just push the torque down some in relation with rpm..(ex...lets say 3.55 give you 300ft/lbs at 3000 rpm and now you have 4.30's and you reach 300 ft/lbstq at 2500 rpm) does this make sense?

dlarge122878

I hope you have a tuner to correct the spedometer with after you install the gears!

Diabolical!

Why do people always say that 3.73s and 4.10s are meant for either a manual or an automatic? It's the most ridiculous thing I've ever heard. Also, why do people only consider 3.73s and 4.10s? I've only noticed this phenomena on the internet, and on the internet, 99.9% of advice I read about gears is just plain bad advice. Gears should be chosen based on their application. For example, I run the 1/4 mile. When I choose my gears (after I've finished all of my supporting mods), it will be based on what gear ratio puts me across the 1/4 mile mark closest to the end of 4th gear without having to shift into fifth. This will require several trips down the dragstrip while datalogging to compute which gear will work best. End of rant.

.boB

Notat all. Peak torque will occur at the same rpm as it did before. And the torque curve will maintain essentiallythe same shape. The torque curve will be higher, so the area under the curve will be greater.

But, it will change in relation to vehicle speed. Because now you're at a lower speed for the same rpm. As long as you shift by the tach and not the speedometer, it will be the same.

Nineinchnail is exactly right. Choose the gear based on the application: 1/8 mile, 1/4 mile, road course, cone dodging, 5.0, 427, 2.3, etc. Unless the car is dedicated to a single purpose, every gear choice is a comprimise. Good for the 1/8 mile, not so good for commuting on the highway. You want the engine in it's power band when it's doing whatever it is you want it to do.

crashed1st2

oooo.. ic.. but what about the 3.90's?.. bc one day (like 10 years from now.. lol) i would like to get blown.. so that might be a good median..

even tho by that time.. i would prolly be ready for new gears anyways
maybe one day you will get blown. ahahahahahahah

Gene K

Gear Ratio does two things changes rpm for a given speed and multiplies torque. However you dont see it on a dyno because the multiplication is backed out. IE they give you the numbers without the gearing effect.

Since anytime you use gearing you introduce friction and the higher the ratio the more friction lower gears (higher number) such as 4.10's will show a lower hp number on adyno all else being equal.


3.90 is available for the 8.8 but just like the 4.30 their are no factory Ford produced gears in that ratio. Only Motives.
So it depends on how you feel about the noise issue and whether its set-up (much harder with Motives) or the finish on the gears.
All I know is my Tech's Wife's Car is noiseless with the Motive 4.30's. He does prefer Ford Gears if available in the preferred ratio because of the easier set-up.

MTAS

Too bad I won't be able to make the get together this weekend (19th) or I'd be happy to let you drive my car. I have FRPP 4.10's/5-spd manual. However with the taller 295/45/18 tires I have, they're basically 3.90's now. Go with 4.10's - you won't regret it.

GTstangB.F.D.M.

ooohhh.. wow.. is that true?.. bc i also have the 295/45's.. and when these run down, im going to try and fit a 305/40 (or something close) drag radial.. so if you have that tall of a tire, it brings the gear ratio down?!..

maybe i will just go with 4.10's then..

i mean my plans for this car is not to be a road trip car.. so im not tooo worried about high speed RPM's.. i mean i do commute on the interstate, but whatever.. and in a year or two, i will be buying a truck, and make this my project car.. and plan on keeping forever..

thank you guys for the help!