ClassicCar

Allan, was the OD from a '51 or from another year car? That's important because a '51 or earlier OD needs a little reduction box for the speedo cable. '51ODs had to have this 2:1 reduction because they still had speedo drive gears same as '50 and earlier, but the '51 cars' speedo calibration was changed from '50 (Hudson was getting finally getting in step with everyone else, going to speedo reading of 60 mph at 1,000 rpm on the speedo cable vs. the 2,000 rpm used up through '50. So if your OD is '51 or earler, the first step is getting that little box, either an original or a modern substitute. If you have that, or if the OD is post '51, then the proper speedo pinion gear for an OD car with 4.11 axle is 448215, 16 tooth. They're not easy to find these days. Al Saffrahn is one of the first to check with.

Roger, my original '51 parts book shows the 16 tooth pinion for overdrive-equipped cars having 4.11 gears, and 15 tooth for 4.11 cars without OD. No guessing required.

No argument on that, Roger ... one really has to look closely on that larger chart.
And please note, my original post is slightly modified (Allan didn't say what year the OD was).

For any folks who are sending a '50 or earlier speedometer for repair and/or calibration, be sure the shop is aware that Hudson calibrated for 60 mph at 2000 rpm for the cable, not 1000 as everyone else did. Some shops don't know this, and you get back a speedo that's way off in calibration.

Since it's a single-lever tranny, it's almost certain to be a '51 or earlier. Mine has a late 1950 casting date on the RH side of the main case. If it needs the reduction box, you'll know it right away when the speedo reads twice as high as it should!

Dave, don't worry a bit about running a 4.11 with overdrive in that car. My '47 C8 with that gearing still accelerates strongly in 3rd overdrive. Your car is a bit heavier, but not that much. I can't find that SW number either. May be from a non-Hudson car.