I'm figuring that right now I could top out at about 195. My questions is, if I were to get a 4.10 gear ratio... Would that lower my top speed? According to the chart, a 4.10 gear ratio in 6th at 6700rpm could take me to 255mph, so either way I would run out of power before gear. Would 4.10's slow me down???

 

Going to a lower gear will always lower your top end unless you have the power to pull through the gear.

 

doesn't make sense? Doesn't it make it easier to pull through the gear? or do you mean to pull through sixth? (magikman on girlfriend's comp)

 

I was under the impression that the higher the gear, the more HP it uses up, kind of like a bike. Even if you have tons of power, wont it still lower your MPH considerably? It should produce less dyno power too, but the curve should change,

I am no expert... any other opinions?

 

yeah man..with that high of a gear its going to make you lose your top end speed. That gear is for down low pull. Sorry to hear about rear dude! Keep me posted

 

With higher numerical ratios you'll get there quicker but will have a lower top speed assuming you have the power to reach redline in 6th gear.

 

However... since either way I don't have the power to pull to redline in 6th... my top speed will be the same?

 

Let's say that it requires XXX HP to top out at XXX MPH. Let's also say that your engine can just barely produce this required HP. Then you simply select whatever gear that puts your engine's RPM at that peak HP level. Obviously too high or low of a gear will put your engine at a lower HP number and you will not go as fast.

 

This question is simple:

Would 4.10 gears lower his top speed considering the mods in his sig?

 

what is your CURRENT top speed you have hit and that you are worried about loosing?

thats the real question? lets disguess a real number not a hypathetical one.

 

I'm just curious so I can better understand...

 

the answer is yes

 

I'm not smart enough to answer this question without more info (even with it I'm probably not smart enough) thus I'm not going to try. But if I were to try I would need more info like, how was this hypothetical "195" MPH estimated, what gear, tire diameter, engine RPM, at what RPM does the engine produce its peak HP and how much? There is much more info that is needed and even then, you won't know for sure without testing and then the results will very from location to location and day to day. It is possible that a 4.10 ratio and transmission gear combination could put the engine's peak HP at some higher MPH in a certain gear.

 

ok no the gear will not lower YOUR cars top speed. going from a 3.42 to a 4.10 would lower the top end if you could redline 6th. BUT YOU CANT. the 4.10 makes it easier to pull threw the gear. and sence the car is aerodynamic, and power restricted. NO YOUR CAR WILL BE FASTER OUT OF THE HOLE AND YOU WILL NEVER SEE THE DROP IN TOP END. if 6th at 6700rpm's is 255mph, you will never get there with your mods, or even close. so gear is not the limiting factor. I have 4.10 in my f-body, and had it well over 150mph just for your personal information

 

Im with Pontiac on this...I Have 4.10's in my car and have ran close to if not a little over 150...the trade off wouldnt even be a thing to think about..I guess after you get beat by someone you could tell them you could run 250 MPH...and then lets say you could, you better go read one of the 70 threads about Aerodynamics put the 4.10's in gain some performance and not worry about some magic number.....

 

I think you are getting yourself confused here.

A higher or taller final drive ratio (gear) will have a numerically lower number, so 2.73 is taller than 4.10

Top speed can vary greatly on setup, it's about matching the power/toque of the motor with gearing, aero drag and weight of the vehicle.

So a taller final drive ratio may or may not affect top speed, or indeed it may have no significant affect at all.

Nope not at all, the curve respresents the engines delivery of TORQUE which is then derived into HP. An engines profile should remain the same regardless of whether it's attached to a gearbox and drivetrain or completly stand alone such as on an engine dyno as opposed to a chassis dyno.

Also when a vehicle is put on a chassis dyno you will dyno the car in a gear with a 1:1 (or as close as) ratio. Meainig that for every one revolution of the flywheel the output yoke on the gearbox (and thus the propshaft) will also turn one revolution. The amount of power being delivered to the rear wheels would only vary thru manufacturing tolorances and frictional loses.

The only time dyno numbers can be confusing is when a high stall torque converter is un-locked, as a torque converter multiplies torque.



As to the original thread posters question, how fast do you want to go? With stock sized tyres and a 6000rpm red line you should see just over 150mph in 5th with the 4.10's, I would assume the car would still pull in 6th, but due to the internal gearing of the 6th gear ratio I do not know how well. Even the C6 Z06 makes it's top speed in 5th and not 6th and it has less weight and more power.

If 1/4 mile and sub 140mph capability are your main goals then 4.10's sound like they should work well. However if you want to see 150mph+ then 3.73 or 3.42 maybe the better bet. However the cost involved may not be justified by going from 3.42 to 3.73

A short final drive ratio will give snappier in gear accelaration but it will hamper high speed work and require more shifting. That's why when I upgrade my 10 bolt I'll probably go 3.08 or maybe 3.42 (I'm auto so it's slightly different) but the principle is the same, I don't want to loose out on the high speed stuff.

 

with 4.10's 5th gear tops out at 172mph... at 172mph in 6th I would be at 4500rpm and at 4500rpm my car is at peak tq as well as 350rwhp which is pleanty of power to make sixth pull

 

my bad, does the Corvette use different internal gearing to the T56 in an Fbody? If so that would explain it, the Fbody uses:

1st - 2.66:1
2nd - 1.78:1
3rd - 1.30:1
4th - 1.00:1
5th - 0.74:1
6th - 0.50:1

So with a 25.66" tyre and a 4.10:1 final drive ratio 6000rpm in 5th would equal 151mph, the same speed in 6th would be just over 4000rpm but with that 0.50:1 ratio I still think it would struggle to pull much, even with 400rwhp. However I can see ~175mph being possible, but this is all suposition as I have no prove or expericence in this circumstance.

 

my redline is 6700rpm