92 GMC K1500 Speedo Problems

[AlbertaClassic]

Hey all, I'm hoping you are able to help me. I am a little stumped on what to do next. I have a 92 GMC K1500 with the 350 and auto trans. Has the magnetic speed sensor. Anyways, my speedometer will not work for most of the time, however will randomly start working and works great when it does. Shut off the vehicle, and back where I started. I tried replacing the VSS, as well as the gauge cluster and DRAC/VSSB with known working ones from the same year and part #s with no success. Mostly no lights on in the dash, however occasionally the parking brake light will be on or check engine light very briefly. SES has not been consistent enough for me to pull a code. Do I have a bad ground somewhere or what could be wrong that it comes and goes like it does? Have tried replacing every component I can think of and making sure all connections are tight. Other gauges work perfect, with no odometer/trip meter or cruise operation. Any suggestions are MUCH appreciated!!!
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[Mr_Rich]

The gauge cluster on my '89 does the same thing. I took it out and re-soldered the specific connections for the speedo and oil pressure gauge and they still behave erratically. I have a spare gauge cluster that I'm going to try eventually but until then I give the face of the cluster the old "Fonzi rap" when it drops to "0" when I'm driving down the road. When it does this the engine changes tone also because the speedo is tied in to the fuel mixture settings. The speedo starts working again and is usually good for the rest of the day. When it gets cold it fails more often so I'll probably have to replace the gauge cluster finally by this winter.