Ok the problem I am seeing is the newer motor uses a hall effect sensor for the VSS, the hall effect is a digital signal that is sent to the ECM at 4 pulses per revolution. Now the problem lies on how the systems work. Usually on the hall effect sensor the ECM would send a voltage out on the signal wire, and as the hall effect is running it effectively grounds the wire. The computer see the ground as one pulse. The VSS in the cluster on the older trucks are just a switch that turns on and off, since one end is connected to ground I am assuming that the ECM is sending out 12v on the wire and is being grounded. I did not test this fact on mine, since the 97 and 89 had the same component test for the VSS in cluster, so I just hooked them up and called it a day.
Might have to check the VSS + wire on the ecm to see if there is voltage on it, if there is I think it will work fine hooked to the cluster, if there is no voltage, it is looking for voltage being sent by the transmission mounted hall effect VSS and the cluster will not work, well not as a direct hook up.
