On 87 and 88 s10 the speed sensor or vss is under the dash atached to a bracket it is a blue box about 3 inches square. It is not on the tail shaft or t-case on a 4x4
It would depend on what year the vehicle is.
I have a 91 s10 and it has a speed sensor. It is located at the rear of the tranny on the drivers side
It is inserted into the rear of the transmission's extension housing, in line with the drive shaft. The back up light switch is higher than the driveshaft.
You will find it on the tail extension housing of the transmission.
it basically tells the computer that the camshaft is turning same as crankshaft sensor. if the sensor does not work the vehicle will not start.
Disconnect the electrical connection from VSS (Vehicle Speed Sensor), remove small bolt holding the VSS bracket in place, remove VSS by gently twisting and pulling out at the same time. Clean area and lubricate the "O" ring on the new sensor before installing it.
It could be the crank sensor, depending what year vehicle you have.
There are several O2 sensors on that vehicle and they are are threaded into the exhaust system at various points.
Sounds like the speed sensor is bad.
If you have a electrical speedo you don't have a cable. Change the speed sensor in the trans.
Speed sensor is located on the tail of the tranny. On the side near the drive shaft. There is an electric connection that clips onto it and is held in by one 10 mm bolt.
There are several O2 sensors on that vehicle and they are all threaded into the exhaust system at various points.