Is it possible to arrange a gear combo, that would allow you to have good pull 1 through 4, and then have a wicked highway gear for the 5th gear??

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Godti
'89 Trans Am (Red)
305 TBI 5spd

 

i'd say 3:73 is about as good as it'll get for you. all depends on how much gas milage you're willing to give up.

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ICON Motorsports
1st & 3rd

 

How much gas mileage will I lose with 3.73?? I was planning to go with the 3.43, I figured what would give me a good launch and a fair mileage.

 

There's not a great deal of difference between 3.42s (there are no 3.43s) and 3.73s as far as gas mileage.

The carb HO cars like mine came from the factory with 3.73s. I dependably got 22 MPG on the highway with the original 305 and those gears, sometimes as high as 24. And that was with a T-5 with the .76 5th gear; I think your car (being a TBI) probably has the low-perf version of that trans, which has a .63 5th. Your mileage should be better than mine was, at least in theory.

How much gas mileage you will "lose" depends greatly on what combo you have now, and on how and where you drive it. My guess is that you have either 2.73s or 3.08s. Compare your current figures with mine, and you should be able to get a rough idea.

BTW, on the gear ratios: they are all ratios of integers. That is, there are whole-number numbers of teeth on each gear, not fractional teeth, so only certain ratios are possible. Usually at least one and sometimes both of the numbers is a prime number such as 11, 13, 37, 41, etc. For example, 3.73 gears have 11 on the pinion and 41 on the ring (41 divided by 11 = 3.72727272); 3.42s have 12 and 41; 2.73s have 15 and 41; 4.11s have 9 and 37; etc.

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"So many Mustangs, so little time..."