I recently went with a lower gear ratio trans, and currently I am now SLOWER at the the 1/4 mile track than I was before!!!
I will be faster, eventually, I hope, as soon as figure out the new variables for the hole shot and shifting into 2nd without going up in smoke.
If you already have trouble hooking up, lower gear ratio's will make it worse. Thats why a lot of folks, with low gear ratio's, get a better ET starting out in 2nd gear instead of first. But that does tend to fry your clutch, rather than your tires.
One of the worst gear ratio combo's that is fairly common is a T5 trans with a 3.27 (or is it a 3.35?) first gear and a 3.5 rear gear. Great for smokin' tires, looking good, playing around. Fairly worthless on the strip without some serious slicks to hook it up.
T5 with a 3.91? What??? Top speed in first is what, 25 mph??