2003 Ford Focus transmission problem on 2003 Ford Focus

While driving and getting up to speed the transmission slips out of gear and then jolts back into gear when you slow down. What is the cause of this?

Asked by for the 2003 Ford Focus
Next ?most ? obvious question(since camster beat me to the first) Is it THE CORRECT FORD FLUID. I put that in bold print because I've seen what even the 'better' aftermarket fluids can do to some A/Ts.NOW the third not obvious to some .....question, I presume since you didn't mention it , that you have no check engine light on. That does not mean that there are no codes stored in the TCM (trans. control module )which in many cases , unless it's a failure that directly affects the emissions system(as the EPA sees it) it will NOT turn on the check engine light , and will not show any specific trans codes with a generic OBD2 scanner. need to have it scanned properly to make sure it's not just an electrical problem(sensor/switch) causing the symptom. Yepster , still haven't found that delete button! good luck.
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I'll ask the obvious question.Plenty of fluid?
Yes, plenty of fluid, the stick shows full when checked Hot!