faulty circut board replace it
at the tail of tranny
You didn't mention what year the S10 is but, yours probably doesn't have a cable driven speedometer. It is electronic.
Broken tooth in speedometer head. Replace speedometer head
you need a new instrument cluster about $350 same happened to mine.
If both the speedometer and the odometer work on and off, I would blame the vehicle speed sensor. If only the speedometer is acting up, I would blame the cluster.
In our 96 Blazer S10, it was behind the radio. We had to remove the radio to get to it.
its inside the distributor.
A 1987 s10 Blazer 4x4 weights around 10.6. This is going off curb weight.
there is none its a sensor at the rear of the trans that sends a signal to your digital dash
Yes,
no you need one off at least a 1988
If it is electronic (not cable driven) and both the speedometer and odometer are not working I would suspect the VSS (Vehicle Speed Sensor) is faulty. The VSS can be found on the tail end of the transmission. If only the speedometer doesn't work I would suspect the dash cluster has to be replaced with a new or good used one. Really need to know what year S10 Blazer you have.