Quote:
Originally Posted by Redog
I've been doing a of of reseacrh on this in the past.
The 3.61 is going to rev the motor higher than the 3.29 when cruising at highway speeds. For me I was looking at what the car is going to cross the finish line at RPM wise.
With the 3.61, in 3rd, I would be in the area of 5500 RPM's vs around 4500 area with my current set-up. I could leave it in OD for the run but the shift points are still going to be high. I figure with the cam I'm going to use, and the fact the car is going to rev higher and quicker, plus crusing RPM @ 70 with the 3.29 will be about 2350 vs 1950 with the 3.05 right now. It will make it a very nice street/strip car, and more than likely in the high to mid 13's no problem (after the rebuild). Plus top speed of my car with the 3.29's should still be in the high 130's which I will never hit in a 1/4 mile. With the 3.61's it's only in the high 100's which is possible to hit after the rebuild and better gearing, if my goal is 13 flat
If he has his motor built and is driving the car to the track, 3.29 is a good gear to have. If he's building a "street" racing car / Fast and Furious / or track only car, sure go with the 3.61, hell go 3.90. Of course your top speed is going to suffer the higher FDR you go.
There are tons of these calculators on the net. I always use the one that is gives you the speed at the RPM after you plug in all the numbers including tire size. I can't find that one right now. They are for RWD cars, but I found that for a FWD car, they are pretty close, but not dead on (maybe off by 300 RPM or so)
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Is it wise to drive continuously throughout town, or on the highway on flat roads in third gear? I hope that makes sense. It just seems like it would be bad to drive in one gear other than (drive) constantly, but I'm sure that is what they are for.