has anyone experienced a failed axle speedometer sender?

i ask because a 1990 i am finishing up had and intermittent speedometer which jumped above 15mph and then would stop below. the odo worked.

now nothing from either.

1. the wires from the sender to speedometer are intact and show continuity
2. i have tried 3 clusters k9800 non abs two of which i know for 100% are fully working..........nothing when plugged in for either
3. i removed the sender and thoroughly cleaned it.
4. i ran two wires from the from 2 connectors at the sender and shorted them as fast as i could with engine running, tap tap tap etc and found the speedometer moved a tiny bit to try and show speed as did the odo

does the outcome of 4. suggest the speedo is in fact good but my limited pulsing is not quick enough to generate the speed needed to generate a higher registered mph?

and if so does the actual axle based sender sound defective?

these old style senders are hard to locate. will a new abs style work on a non abs axle IF i also change the axle cover?