I think a 3.00:1 or up to a 3.50:1 would be good, if you ran the taller gears like 4.11:1 you would be turning about 4,000 rpm at 70-75 mph. Here's the formula MPH= rpm x (tire radius in inches) divided by (axle ratio x 168). Here's for 3.50 @ 3500RPM: 77.38mph = 3500 x 13 (for a 26" tire) divided by (3.5 x 168). A taller gear is for performance is great for increasing your torque multiplication output, but decreases your gas mileage and increases wear on the engine. Good Luck.
I cant stand my car in fourth gear going 60 miles an hour. and i have a 2.79 rear. Id probably die if i witnessed 4000 rpm down the highway. i mean thats screaming. Stay with a 3.00 if you are concerned with highway.
My 3.50:1 is too low (High numerically) for extended highway driving in my opinion. A 3.00:1 would be a good highway gear yet still adequate for a little grunt off of the line with your combination. The final drive ratio on a standard old school 4 speed is 1:1. The same holds true for a C4 or C6 auto trans.
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