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i got a built 62 with the stock 3.00 gear and cruise-o-matic trans,she runs good but going down the hwy at 55mph she runs tight,so iam looking for a good hwy gear so i can run 75 with no problems,but i dont want to go so high that it has to pull hard out the hole,,so let me know what u guys think,,thanks
 

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"Tight"? Not sure what you mean by that. Remember, everything is a compromise, so you'll give up response and acceleration for reduced highway rpms. Typical rpms for 3.00 gears at 70 mph is about 2800, 2.75s about 2500, and 247s about 2300 rpm. Also don't forget that while the higher gears should improve cruise mileage, it can also hurt mileage in-town with more throttle required to move the same with traffic. If you just putt around and flip the bird at impatient drivers, then you may see overall better mileage.

David
 

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I love the 2.75 on mine but you aren't going to outrun anything from a dead stop with it. The 3.00 is a good medium rear. I am a puttputt and wanted better fuel mileage on the highway so went with 2.75. It isn't really bad in town either, just don't expect to hit the gas and take off quickly, good things take time. :) I'm totally happy with the 2.75. My 390 isn't built, bored .040 over, RV cam is bout it.
 

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ShotRod has the same set-up as I do (in my '70 Mercury conv.) and the 2.75 rear end is stock for my car, but I wanted to try a 3.50 a while back. Installed the shorter gear set, drove the car for a few months, then went back to the 2.75s...too much freeway RPM with the 3.50s, IMHO. Even with the 2.75s, my car will spin (one) rear tire with no problem at all because of the peg-leg differential, but it still accellerates fast enough for me, especially when you force a kick-down.
 
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