You have a 92 gmc vandura and occasionally the speedometer shuts off and then it wont shift into the higher gears you am told this is a speed sensor issue is it If so where is the speed sensor located?
I have a '87 GMC Rally STX van, but I think the vehicle speed sensor is similar; The sensor is located just behind the speedometer in the instrument cluster on the dashboard. You access it by removing the instrument panel (carefully). You will need to disconnect the speedometer wire and the electric socket before pulling the instrument cluster out. The vehicle speed sensor is a very simple and reliable component. Not likely to fail. From what you say about the speedometer 'shutting off', I would be inclined to think there is something wrong with the speedometer wire. This component won't last for ever and is probably worn out. Unless your transmission is electronically controlled (don't think the '92 models were), I don't think replacing the speedometer wire will address your transmission problem. I believe that is sorted out within the automatic transmission unit. The TV-cable must be intact and correctly adjusted for the transmission to shift correctly. The TV-cable connects the throttle with the gear-box. Hope this is helpful information.