The speedometer quit working and the transmission

I had a similar issue with my blazer. I lost speedometer,tranny, and a bunch of other things. There is a pink and brown wire which all runs for ignition. I found out that this wire which connects alt, tranny, speedometer and other things was bad somewhere through out the vehicle. Had this fixed and everything is running again. If you look at the alternator you should see the pink and brown wire. Where to start to find the problem area on the wire is pretty difficult. I could be wrong, but when i lost those very 2 things at the same time among others. This was the answer to the problem for me. Hope this helps!!

It sounds like the Vehicle Velocity Sensor (V V S) has gone bad or the wire harness has gotten damaged due to corrosion. The V V S sends signals to the ECM which will indicate to the transmission when to up and down shift according to the engine speed and will send signals to the speedometer. The sensor is on the driver's side along the tail shaft if the transmission, good luck and keep me posted. Auto Zone will have the sensor and give you the step by step instructions and should take no more then 15 min to replace, it's held on by one bolt and the wire harness just unclips.

They are related. The speed sensor is located at rear of the trans, just before the driveshaft. maybe the connector came off, or the sensor is bad?