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SO....Speedo reads ZERO, but the ALDL data is showing a vehicle speed when i move. Thoughts? Could this be the cause. I first assumed it was the speedo bad, but could it be the VSS thus preventing upshift?
Diagram shows the VSS feeding the VSS buffer which then feeds the ECM and instrument cluster separately so it seems to me if the ECM is getting a speed signal, it should be happy with it.
Ill double check the TPS but im pretty sure that was working properly. This is a total rebuild/restore Frankenstein truck lol the engine is the only thing i know works. So im testing components as i go. Any clue what to read to test my speedo?
Can you describe what all is mixed and matched? Your stock cable driven speedo won't work with an electronic VSS. I think the 87 trucks had a VSS that allowed the cable to be threaded into the ass end of it. Is the harness mixed and matched? How about that speedo box? I think it was called a DRAC. There's a good chance something isn't wired right, all this time I kept thinking it was just an R&R&R.