I have an 89' GMC C1500 just had my (already rebuilt) transmission rebuilt. 1st time was August (2016), then 2nd time was last week (02/20-02/24/2017) My speedometer hasn't worked since the original transmission was in it (pre-August 2016) the gear on the tail shaft is good, the gear box that connects the cable to the transmission is good, I do not know where to go from there. I tried checking the fuse, but apparently my truck doesn't have a fuse for the speedometer. I was told it could be a DRAC module truck or a PCM truck, a local GM Dealership Service told me it (should) be a PCM, being 89'. 94' and newer were DRAC Module. All the other gauges work except speedometer, odometer and tripometer. However, my Speedometer and odometer do move at times on their own, not sure how or why. Leads me to believe they work, its just something else that isn't working. Has anyone ever experienced this problem before?