Whenever I happen to report a sentence that's originally in the present perfect, I switch tenses accordingly, transforming it into the past perfect. My problem though focuses on the backshifting occuring in utterances that utilize the simple past. I know that I do not have to switch tenses when the sequence of events is clear and obvious, as in:
He told me he had an accident on his way to work.
But does the same apply when no additional time frame is provided?
He told me he had an accident.
Or should I use the past perfect there for the sake of brevity? Is there any instance in which one form is more prefered? Or do sentences like:
He said he went on a trip to Japan.
He said he had gone on a trip to Japan.
have exactly the same meaning?