The Stovebolt Site Forums The Shop Area Driveline T5 Conversion

I now have a running and driving 1942 3/4 ton, with a nicely operating T5 trans. Thanks to all who so generously helped me through this swap. All seems good. I only need to take her for a good long run to check every phase of operation. I do have a problem that is challenging me, and that is my speedo driven gear selection. I went through the calculator and I got a recommendation of a 24 tooth gear. I wasn't able to find a 24 tooth gear, so I installed a 22 tooth, as it was available. My truck has a 4.55 OE 1942 differential. I'm running 600-15, 6 ply tires, that are 29.4 inches in OA diameter. The T5 I installed (1352 042) has the red drive gear in the tail housing. Today, I drove the truck through one of those radar devices the police put out along the road. At an indicated speed of about 50 MPH, the radar showed me 37 @ MPH. Clearly, I do not have the right drive and driven gear combination for my set up. I did buy a set of drive gears with different tooth counts so maybe if I replace the 22 tooth with a driven gear that has fewer teeth, I can get a more accurate speedo indication. Any advice is appreciated.