Swapping a rebuilt rear end into my 1972 Skylark. It was a non posi with 2.56 gears ratio. I had the rebuilt set up with 3.73. Anyone have any idea what speedometer gear I need to order to get me in the right ballpark. I know my tires will make a difference, but would like to start in the right range while I'm breaking things in. Any and all feedback appreciated.
have a look at this thread, http://www.v8buick.com/showthread.php?309526-speedo-gear-size&highlight=speedometer+gears http://www.buickperformanceclub.com/speedo.htm You need to know 3 things to figure out the gears you need, The number of teeth on the DRIVE gear, the rear gear ratio, and Tire height. You can use this calculator, http://www.tciauto.com/tc/speedometer-gear-calculator/ The 72 Skylark with 2.56 gears had a tire that was about 27" tall. It had an 18 tooth DRIVE gear, and 35 tooth DRIVEN gear. That's assuming the transmission in the car is the same one it left the factory with. If not, the DRIVE gear might not be 18 teeth. In any case, the gears may not be available for that combination. You may have to use a ratio adapter in line with the speedometer cable. https://transmissioncenter.net/shop/54ra2-gm-dodge-ford-ratio-adapter/ https://transmissioncenter.net/shop/gm-dodge-ford-ratio-adapter/ https://transmissioncenter.net/shop/gm-dodge-ford-ratio-adapter-other-ratios/
Until you figure it out, just get the free speedometer app for your phone. Take the car to Guptill's and enjoy an ice cream. UticaGeoff
