This one should be quick for you guys. I am needing to change my differential to a ford 9" and have to pick out some gears. I have 3.07 and 28" tires, so i was thinking go with a 3.50 and get 32" tires to keep the speedometer accurate. Then later i realised that this would be the same thing to the engine, meaning the engine is still spinning the same amount of RPM at the same speeds. Is there any advantage of having 3.50's and 32" tires, rather than 3.07 and 28" tires, or am i going to have to recalibrate the speedometer and get some 30" or 28" tires? thanks
If you change rear gearing, then compensate by changing tire height so that the speedo reads the same, you've gained nothing other than spending a ton more money than it costs to buy one or two speedo gears. If you are looking for a 1/4 mile drag car, it's not difficult to estimate rear gear/tire height needs if you know vehicle weight/engine output. If you're just looking for something to tool around in & smoke tires, gear selection is pretty much up to you. Once you know what you want you can figure out which speedo gear(s) to buy. The first six words of the previous sentence are the key! Devon
Well... Might as well set it up for a 1/4 mile car, but we "were" planning on just a cruisng car with the ability to take it to the drag strip, until we wanted 10.75 cr with 650 HP I was thinking about buying 3.50's because then my top speed would be right around 143 MPH at 6000 rpm, putting me at or around 5700 rpm at the trap with 28" tires. i figured a 10.5 second car should finish around maybe 135-140, that is if i can get a heavy beast car to go that fast, if not, time for a diet
