Speed Sensor? Cluster? Burnt out Gears?

[Svanky10]

91' Conv. Camaro RS / 305 / V-8 / Automatic Trans. 700R4...... Somebody Help Me!! Alright, had the tranny worked on several occassions, actually the torque converter (six times), kept going bad for some reason? Anyway, last time I brought it in. The car drove fine..... 300 miles later the speedometer started to fluctuate eventually quiting all together. I replaced the speed sensor thinking that this might be the problem however it is not; unless i have a faulty speed sensor? Now i'm at a loss. Could it be the cluster or a burnt out gears inside the tranny?