fullsize speedo not working

Hey i was wondering what i could check to see why my speedometer isn't working, my rpm gauges works and every other gauge, is there wires going to the tranny that tell the cluster? or is it mechanical? its a 1995 fullsize 1500, i did a cut floor body drop so maybe i cut through the wire or something? lol

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check the speed sensor on the tail of the tranny, mine is acting up too, jumping around and stuff.

if the speedo is jumping around would that be the cluster or the sensor?