I found those yellow & purple wires(also a ppl/wht wire). I even labeled them "old trans wires" and capped them off & tucked them in my harness coming from c-100. They must have been a 3 wire plug. Anyway I connected the speedo wire coming from my pcm to the yellow & purple wires as chevy-art said and I still have no speedo. Not saying chevy-art is wrong,cause it worked for him. I must be doing something bass ackwards. Might have to pull the cluster like farmtruc said. Thanks. Still scratching my head!