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Transmission seems confused

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I bought this car,'96 Deville, with a locked engine. Replaced engine. Trans would only run in low or reverse-Replaced sift kit. Transmission overtemp warning would come on, 0218 I believe. The transmission shifts smoothly at various throttle angles and does not foam or blow the fluid out. Engine temp remains steady/normal at all times. About a month ago the trans. over temp code stopped coming on and it started setting, 0716-Input speed sensor out of range or 0717- Input speed sensor. At times the codes will set immediately, within five feet, at others times it may take 40-50 miles before any code is set. You may only get one code or you may get two, or on occassion you will get all three codes at the same time. Torque convertor slipage is under 2%. The trans. overtmp. code just started coming on again about ten days ago. If the Trans. overtemp warning light didn't come on, you would never suspect a problem with the trans. I have driven the car as far as 50 miles, at speeds up to 90MPH without getting a code only to have it light up two or three codes before I get out of my driveway the next time I drive the car.

The local Cadillac dealer said that," it could be an internal leak or low line pressure caused by the speed input sensor." but they couldn't be sure until they took it apart.$$$$$$$$$$$$$$$$$.

Could there be a leak in the lower valve body due to a bad seal or improper install? Will Input speed sensor cause Trans. over temp. by not providing input for line pressure adjustment?

My suspicion is that the shop that changed the engine chiseled at least one of the flexplate bolts off, since the engine was locked, and may have damaged the torque converter in the process. This would possibly account for the overtemp,however it would seem to me that if the transmission was really over heating, it would also cause an increase in eng temp. Also, I had a '95 Seville with a bad input speed sensor and it was noticeable, especially during downshifts or when shifting below 30MPH.

Any thoughts or comments would be greatly appreciated. :(

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I would check wiring routes. The sensors are very sensitive to electrical current. If wire harnesses were not routed properly stray current could cause codes to set. Check the harness locations, connections, and grounds. Make sure no spark plug wires are touching any wiring harnesses. Some sensors are even sensitive to high powered two-way radios.

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