757GT

3.90s turn about 2900 at 80.

don_w

Here is a formula for determining the rpm your engine will be at for a given speed:

RPM = GR X MPH / Dia / .002975 (GR is rearend gear ratio; MPH you make up; Dia is rear tire diameter in inches - let's assume 26.5" here)

For example: 3.73 X 80mph / 26.5" / .002975 = 3,785 rpm
Or, 4.10 X 80mph / 26.5" / .002975 = 4,160 rpm

However, that calculation would work for 4th gear (1 to 1 ratio) but not with overdrive. With a 5-speed automatic, 5th gear is 0.75 OD and the manual has a 0.67 OD. So, multiply your OD times the rearend gear ratio to come up with the final gear ratio, as follows (for the automatic):

(3.73 X 0.75) or 2.7975 X 80mph / 26.5" / .002975 = 2,838 rpm
(4.10 X 0.75) or 3.075 X 80mph / 26.5" / .002975 = 3,120 rpm

Personally, I'm liking the idea of 4.10s even better now. I can still make the 300-mile cruise to Las Vegas without a problem (except for maybe a speeding ticket or two).

silverbullit05

personally i am not going to swap gears till i get a 6 speed so i can still have some good top end and a low end as well. just me though.

n4ggs

how about a 5.0 rear diff and the top 3 gears are all overdrive!

kcshaner

Anyone with the 4.10's notice a differnece in MPG.....please share your findings

Loomis

I have noticed a big drop in gas mileage. At 80 I am running 3k RPM. But I wouldnt havent any other way.

td1320

I have gotten a best of 24 mpg and average between 22 and 20. I turn 3000 rpm's at 80 mph as well. Mine is a daily driver. I have 10,000 miles on mine since mid November 2004.

Loomis

WOW I want your MPG I average 13.

td1320

I've never gotten less than 17 period. You need to put your right foot on a diet.