Toyota Repair: speedometer only works after driving a few miles, faliure, speedometer

Question
94, Toyota, 4x4, five speed manual trans,

The speedometer stays at zero for the first 10 miles or so and then works fine until the key is turned off.  The odometer indicates distance whenever the wheels are rolling.  This vehicle appears to have a sensor and wiring instead of a cable driven speedometer....I am not finding a cable from the transmission to the speedometer.  

Do you know of a common component faliure, like the sensor?

Is the computer involved with speed indication.

What tests can I do to determine where the problem is?

Am I completely wrong.....does this truck use a cable driven speedometer?
Thanks!!
John

Answer
It has a speed sensor on the transmission that inputs signals directly into the speedometer to indicate vehicle speed, both the odometer and the speedometer work off this same signal so if the odometer is working but not the speedo it makes sense that the problem is not the sensor but the speedo itself, the computer receives a speed input signal also but only to for cruise control and other functions, it does not input a signal to make the speedo work.