Timspony

This chart makes perfect sense to me....here's low it works, when installing 3.73's you're going to be spinning the driveshaft 3.73 times per 1 rotation of the tire / hence 3.73:1...so the driveshaft is spinning more then, say with 3.08's or 2.73's (stock gears)...at the same time, this means that your Transmision gear is ALSO spinning more, SO you need to put MORE TEETH on the trans. gear (tooth) to correct it...slow down the spinning of the trans. rotations...

Like the chart shows in you case: 1991 LX T-5, 3.08 = 20 tooth....3.55's (or close with 3.73's) = 23 tooth (24 would be perfect if they made it, but they do not)...Hope this helps!