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Q: Transmission shifted very hard one night and has not done it again

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One evening on way home from work, about 3/4 the way home I stopped at a light then when light was green accelerated and the tranny shifted very hard. It did it a few more times, with the last one being when I put car in reverse from park. It clunked. Next morning, and currently it runs and shifts fine. No issues at all. Should I service tranny, been around 60,000 miles since last done. Thanks

My car has 88000 miles.
My car has an automatic transmission.

Check the level of the transmission fluid. If the fluid and filter have never been changed that would be wise to do as preventive maintenance. Transmission fluid filters can get plugged and clean fluid will promote efficient and long lived operation of the transmission. If the fluid is changed be sure the level is correct, not too high and not too low. Abrupt, harsh, or delayed shifts can be cause by valve body faults (including dirt from contaminated fluid), bad shift solenoids, and internal hydraulic leaks in transmission seals and pistons. If the problem is very intermittent, it is going to be hard to pin down, that’s why your best initial step, to potentially resolve or delay a more serious failure, is to change the fluid and filter. If the problem crops up anew and persists, at that point you would look at the most obvious possibilities first which are shift solenoids and the valve body. Also, it is possible that diagnostic trouble codes have been stored in the engine computer or TCM and those could be sought now during a check engine light diagnostic.

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