Brad and Karen wrote:

> Hey guys, daily lurker, occassional poster writing.
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> I have a 1993 Cobra I just got back from Ford after getting it safetied. I got it last year but there were lots of minor issues with it so I let it sit over the winter. Got it back today and it passed. Finally!
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> I've been driving my 2006 Lincoln Zephyr all winter. The two cars are like night and day. And I don't mean that in a bad way for the Mustang necessarily. It's got it's own charm that's for sure in a "air conditioned seats are for sissies kind of way". (And I think the Zephyr threw a fit today when the Mustang got back home cause she wouldn't start for me. Pouty. So I called the Lincoln-care # and they towed it to Ford. That'll teach her.)
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> Anyway, my question today. The previous owner put gears in this car but I can't figure out which ones. I know about jacking it up and turning the driveshaft, but, I'm too lazy for that... lol. I used the All Ford Mustangs gear calculator and none of the speeds really line up with the RPMS. The calculator says 3.55s in 2nd at 40mph should turn 3700. Mine turns 3500 bang on, which is much closer to the 3400 for 3.27s, but still off a noticeable amount. The other speeds, etc, are off too.
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> I'm thinking maybe the tire wear is throwing it off a bit, but can anyone who has a stock T-5 with 3.55s or 3.27s give me their RPM at say 40mph in 2nd? Or am I asking way too much? lol
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> Thanks guys! Glad I'm back in the fold...
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> Brad
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Not just tire wear, but tire size will affect that method of calculating the
gear ratio. {I'm just guessing that you don't have the original tires. ;-) }

You should get the gear ratio by the ratio of tire turns to driveshaft turns.
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Cheers, Bob