Speedometer Problems

Does anybody have suggestions for things to look at that might cause some odd speedometer behavior? Here's what I know:

The odometer and trip-meter continue to count correctly, as verified against the odo of a 2017 Harley Road Glide, 2003 Harley Dyna T-Sport, and the GPS that was running on the Road Glide.

Sometimes the speedo needle will jump up to read a certain value then stay there, some time later it might go up or down to another value; but mostly it just reads 0.

Shortly after noticing some problems (it just stopped reading speed), the speedo cable actually fell out of the speedo housing. At the next stop, I hooked it back up; and that's when I noticed it would go up to a certain speed then stick there, sometimes changing but mostly not. At the next stop, I hosed it down with some WD-40 but it didn't help.

In the garage since then, I removed the speedo cable and hub on the front wheel to inspect. I didn't find any worn or broken ears in either the hub or the cap with the speedo gear mechanisms. I removed the core of the speedo cable and it was in good shape - no breaks, no rust, and put it back in the cable housing.

I suspect the problem is actually in the instrument pack itself; and I'd welcome some suggestions for what to check and how to check it.

Thanks!

It sounds like a gear issue somewhere in the box itself, like you mentioned. As far as troubleshooting, you've already done everything I'd do..  checking the front wheel pickup, the cable, checking the worm gears, etc. Does the odo work correctly, or is it sped up, too?

The Odometer appears to work correctly, along with the trip.

I figured out how to disassemble the instrument pod - two 8mm nuts on the back, and unplug the harness, then it lifts out - watch for falling washers. Then there's a few obvious screws to remove the shroud, and two to remove the speedometer mechanism.

There's a "pan" that translates, electromagnetically, the turning of the speedo cable into the force applied to the needle. I didn't disassemble that mechanism, but I believe that is the issue. I'm going to take it apart again and disassemble the mechanism this time to inspect/clean it.

Well, I've still no speedometer. Trip and Odo are correct, so the cable is turning properly from the hub up to the instrament cluster.

As nearly as I configure, the translator pan isn't working properly. I tried hosing it down with WD-40, but I'm not getting anywhere.

From what I can tell, the instrument cluster can't be disassembled (to prevent odometer tampering, from the looks of things); so I'm not certain how to proceed. Does anybody have a suggestion?

It doesn't bother me too much, since I can just use the tach, but I'm probably going to be putting her up for sale soon and I don't want to have to tell somebody that the speedometer doesn't work.