Transmission problem
1992 Toyota Pickup 6 cyl Four Wheel Drive Automatic 178000 miles
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While I am driving down the road my truck shifts down to i think first gear. I'll be driving along with no speedometer and the check engine light will come on and start flashing. Just before the tranny shifts down the speedometer will start twitching, it acts like a short, and then it shifts down. I can pull over, put it in park then back to drive and drive a little farther.

We have checked the wires for continuity between the speed sensor and the ECU. And we put in a brand new speed sensor.