ntsqd
heratic car camper
OTOH if starting from a known point and with a specific goal you can figure out what the axle ratio should be. My current project (see Wagon link in Sig) is getting a 5.3L/4L65E/NP241 combo installed in it. I want the PCM to not know that it's been transplanted. I looked up the donor vehicle's axle ratio and stock tire size along with my desired tire size for the Wagon. Entered those into an Excel file to get an rpm vs. mph profile and then worked backwards to an axle ratio that results in the same profile that the donor had. Turns out that is ~4.30:1, so the Wagon's D44's got 4.27's and if I ever move to a rear D60 it will get 4.30's.
