I am using 3.70 gears with my T56. I think you could also use 3.50's and be happy with the result.
What are your goals for the car? All out performance? Cruiser with an occasional trip to the strip? Will never see a drag strip? Road racing?
Your 300 6 sounds built to the 9s. I frankly wouldn't have thought it possible to get the power you describe, unless I'm misunderstanding your post. Maybe you're running 13:1 compression and E85; I don't know.
Anyhoo, knowing your goals will help people to recommend gears. I had a 250 6 in my convertible at one time and I think that engine liked tall gears (like 2.80 or so), because it wouldn't wind out. It had a lot of low grunt but nothing up top. If your 6 really makes over 300 hp it must be winding up to a higher rpm than the sixes Ford built in the 60s!
It would probably be good to post your power band too. For instance, if it's a drag car you might want to go through the traps at the top of your power band in fourth gear. We would want to know what rpm and what size tire to calculate the number.
Too much info?
given the amount of torque you are thinking you have, a 3.50 gear will do rather nicely. your 300 is going to have some monster low end torque due to the 4" stroke, and the mustang is light enough to not need anything deeper.
given the amount of torque you are thinking you have, a 3.50 gear will do rather nicely. your 300 is going to have some monster low end torque due to the 4" stroke, and the mustang is light enough to not need anything deeper.
What i has hoping to accomplish with the massive low end was being able to use higher gear and increase the top end speed of the big six. As you know its not going to have that top end power of the 289 hi-po. by gearing higher I hope to obtain those speeds and power at a lower rpm.
Actually if it makes the power you think it will make it's going to be far superior to a 289 HiPo. I know Ford said a HP number back in the day, but you can use any HP calculator based on the Mustang's quarter mile speed to debunk that number. I think it was common back in the day to over-rate engine HP. Now there are regulations about how to test the engine and the dyno runs are double-checked before the car company can make some wild claim.
have you timed your car through the 1/4?
For a T-56 with a 2.97/2.07/1.43/1.00/0.80/0.62 gearset, and 235/75-15 tires (28.9" dia) 5000 RPM in gear with various final drives looks like this:
Speed in gears
Final ....1st....2nd....3rd.....4th.....5th......6th
2.73.....51..... 74....107.....153.....191.....246
3.08.....46..... 65.....95.....135.....169.....218
3.27.....43..... 62.....89.....127.....159.....206
3.55.....40..... 57.....82.....117.....147.....189
3.73.....38..... 54.....78.....112.....140.....180
4.11.....34..... 49.....71.....101.....127.....164
4.56.....31..... 44.....64......91.....114.....147
5.13.....27..... 39.....57......81.....102.....131
And 65 MPH in 6th gives these RPM
Final Drive
2.73.....1056
3.08.....1192
3.27.....1265
3.55.....1373
3.73.....1443
4.11.....1590
4.56.....1764
5.13.....1985
Obviously anything under 4.56 is pretty much useless unless you're headed to Bonneville
With the TKO the numbers are
Speed in gears
Final.....1st....2nd....3rd.....4th.....5th
2.73.....47.....77.....114.....153.....224
3.08.....41.....68.....101.....135.....199
3.27.....39.....64......95.....127.....187
3.55.....36.....59......88.....117.....173
3.73.....34.....56......83.....112.....164
4.11.....31.....51......76.....101.....149
4.56.....28.....46......68......91.....134
and
Final Drive
2.73.....1158
3.08.....1307
3.27.....1388
3.55.....1506
3.73.....1583
4.11.....1744
4.56.....1935
Which makes the 4.11 or possibly 3.73 look about right
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