Alternator is a possibility.
Take truck to any autoparts store and have charging system tested, battery, alternator, starter draw.
This will tell you if alt. Is problem.
If this happens only when in gear, then you may have a bad motor mount causing excessive engine movement and possibly pulling on a wire harness to the point that it is causing the circuit to be opened.
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Saturday, January 23rd, 2010 AT 10:13 AM