I'm not sure you got the right gear, unless your truck is a 47.1 year. Here's the cross section from the 48-51 shop manual. The gear looks narrower than yours. The sleeve between the speedo gear and the u-joint is not splined, but just holds the speedo gear in place when the front u-joint yoke is secured by the bolt into the shaft. As long as the sleeve is the right length and properly tightened, it will keep the speedo gear turning, as everything in contact with the gear rotates (shaft, inner bearing race, and sleeve). If there's too much load from the speedo driven gear, then it might slip, but that's highly unlikely.
Here's the 1947 transmission cross section also, The same thing applies to the sleeve and how it keeps the speedo gear from slipping.
Last edited by klhansen; 04/02/20258:22 PM. Reason: added picture
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
