I have a 1993 Saturn SL2 automatic with approx 190,000 miles. About 4 years ago the transmission started shifting irregularly. We had a Saturn dealership check out the car and they said there was nothing wrong with the transmission. A little while after that the speedometer stopped working. We have replaced the speed sensor with a new one. We tried a used computer (car ran worse) and a used head cluster, no change. The car starts everytime and runs great except for the problems I described. We use it to run errands and don't take it more than 25 miles from home just in case. I'm not sure how to get this diagnosed. Transmission place or back to the dealership? Can you help?

Optional Information:
1993 Saturn SL2 4cy turbo

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It's in my question