Annoying Speedometer Noise at Cluster

You've got a tight bend in the cable, somewhere,

Were I you,, I'd get the cable down to where you can pull the inner cable out from the top,, clean it,, the as you feed it back into outer housing,, lube it liberally with axle grease, or good lube..

Then reinstall the cable to the speedo,, making sure to avoid any tight turns/kinks,, then check the cables path right down to the trans,, easing any bends as possible..

The speedo jumping 5 - 10 mph is the cable binding,, then springing free..

hope it helps