Some math regarding axle gears.

[shovel]

I put this together for my own purposes but I figured it might be useful for others who are making choices about their SN95. These all assume a manual T5 transmission as equipped in a 1994 Mustang GT.

First table is what I'd consider the usable street driving range of engine RPM. This is completely arbitrary on my part I chose from 1300 rpm to 4500 rpm as that seems like a reasonable range in which to operate the engine within any single gear if conditions are appropriate. I don't care to discuss, make your own table with your own rpm band if you like.

Gear	3.08:1 Axle	3.27:1 Axle	3.55:1 Axle	3.73:1 Axle	4.10:1 Axle
1st Gear (3.35)	10 – 33 mph	9 – 31 mph	8 – 29 mph	8 – 28 mph	7 – 25 mph
2nd Gear (1.93)	17 – 58 mph	16 – 55 mph	15 – 50 mph	14 – 48 mph	13 – 44 mph
3rd Gear (1.29)	25 – 87 mph	24 – 82 mph	22 – 75 mph	21 – 72 mph	19 – 65 mph
4th Gear (1.00)	32 – 112 mph	30 – 105 mph	28 – 97 mph	27 – 92 mph	24 – 84 mph
5th Gear (0.68)	47 – 164 mph	45 – 155 mph	41 – 143 mph	39 – 136 mph	36 – 123 mph

Second table is the road speed at which you'll reach 6000 rpm in each gear. Yes I know nobody's going 219mph in a SN95.

Gear Ratio	3.08:1 Axle	3.27:1 Axle	3.55:1 Axle	3.73:1 Axle	4.10:1 Axle
1st Gear (3.35)	44.5	41.9	38.6	36.7	33.4
2nd Gear (1.93)	77.2	72.7	67	63.8	58
3rd Gear (1.29)	115.5	108.8	100.2	95.4	86.8
4th Gear (1.00)	149	140.4	129.3	123	111.9
5th Gear (0.68)	219.1	206.4	190.1	181	164.6

Third table is the peak wheel torque in each transmission gear, assuming a stock rating of 285 ft-lb from the engine.

Gear Ratio	3.08:1 Axle	3.27:1 Axle	3.55:1 Axle	3.73:1 Axle	4.10:1 Axle
1st Gear (3.35)	2,940 lb-ft	3,122 lb-ft	3,389 lb-ft	3,561 lb-ft	3,914 lb-ft
2nd Gear (1.93)	1,694 lb-ft	1,799 lb-ft	1,953 lb-ft	2,052 lb-ft	2,256 lb-ft
3rd Gear (1.29)	1,133 lb-ft	1,202 lb-ft	1,305 lb-ft	1,371 lb-ft	1,507 lb-ft
4th Gear (1.00)	878 lb-ft	932 lb-ft	1,012 lb-ft	1,063 lb-ft	1,168 lb-ft
5th Gear (0.68)	597 lb-ft	634 lb-ft	688 lb-ft	723 lb-ft	795 lb-ft

And finally this last table is peak wheel torque in each transmission gear assuming a decently put together NA build making 320 ft-lb. This number is arbitrary and does not reflect my specific engine or anyone else's, it's just a number that any NA 302 should be able to achieve with the usual HCI stuff and I drew it up to demonstrate contrast vs. the stock values in table #3.

Gear Ratio	3.08:1 Axle	3.27:1 Axle	3.55:1 Axle	3.73:1 Axle	4.10:1 Axle
1st Gear (3.35)	3,301 lb-ft	3,505 lb-ft	3,805 lb-ft	3,998 lb-ft	4,395 lb-ft
2nd Gear (1.93)	1,902 lb-ft	2,020 lb-ft	2,193 lb-ft	2,304 lb-ft	2,533 lb-ft
3rd Gear (1.29)	1,272 lb-ft	1,351 lb-ft	1,466 lb-ft	1,541 lb-ft	1,693 lb-ft
4th Gear (1.00)	986 lb-ft	1,046 lb-ft	1,136 lb-ft	1,194 lb-ft	1,312 lb-ft
5th Gear (0.68)	670 lb-ft	711 lb-ft	772 lb-ft	812 lb-ft	892 lb-ft

I am not personally invested in what gears other people choose to run or why.

 

[shovel]

Assuming the stock 17" option tire size of 245/45ZR17 on the same car and a weight of 3450 pounds with driver, static weight distribution is about 56/44 which means somewhere around 1500 pounds over the rear axle and a generous 20% weight transfer on launch we can estimate that there's around 1800 pounds pushing the rear tires down. For a high performance summer tire on a good clean surface you can hope for around a 100% friction coefficient which means you can put down about 1800 linear lbs of thrust. Drop that to like 1500 on premium all seasons.

That tire size is 25.7" diameter so half of that is 107% of a foot, in other words if you look at the torque-at-the-wheels chart in the top post and multiply those numbers by about 0.93 you'll get the amount of linear thrust being pushed through the contact patch on the ground.

Example, for a stock 94 GT on all season tires available torque exceeds available traction in first and second gear with a 3.08 rear end.

This is all casual to get us some basic reality checks, we're not landing a space ship on Mars so the level of precision is appropriate to the medium.