dan, (?)
Most of the time, a bouncing speedo needle is caused by the cable. I would take the inner cable out, clean it and then re-install it with a liberal dose of lubrication. Then see what happens.
If lubing the cable doesn't resolve the problem, take a look at the speedo-gear ... remove it from the tranny an dmake sure it is still square... Sometimes they will wear and begin to round out letting the cable slip as it turns ...
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